Articoli di riviste: "Graft copolymers"

1

Roggi, Andrea, Elisa Guazzelli, Claudio Resta, Gabriele Agonigi, Antonio Filpi e Elisa Martinelli. "Vinylbenzyl Chloride/Styrene-Grafted SBS Copolymers via TEMPO-Mediated Polymerization for the Fabrication of Anion Exchange Membranes for Water Electrolysis". Polymers 15, n. 8 (8 aprile 2023): 1826. http://dx.doi.org/10.3390/polym15081826.

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In this work, a commercial SBS was functionalized with the 2,2,6,6-tetramethylpiperidin-N-oxyl stable radical (TEMPO) via free-radical activation initiated with benzoyl peroxide (BPO). The obtained macroinitiator was used to graft both vinylbenzyl chloride (VBC) and styrene/VBC random copolymer chains from SBS to create g-VBC-x and g-VBC-x-co-Sty-z graft copolymers, respectively. The controlled nature of the polymerization as well as the use of a solvent allowed us to reduce the extent of the formation of the unwanted, non-grafted (co)polymer, thereby facilitating the graft copolymer’s purification. The obtained graft copolymers were used to prepare films via solution casting using chloroform. The –CH2Cl functional groups of the VBC grafts were then quantitatively converted to –CH2(CH3)3N+ quaternary ammonium groups via reaction with trimethylamine directly on the films, and the films, therefore, were investigated as anion exchange membranes (AEMs) for potential application in a water electrolyzer (WE). The membranes were extensively characterized to assess their thermal, mechanical, and ex situ electrochemical properties. They generally presented ionic conductivity comparable to or higher than that of a commercial benchmark as well as higher water uptake and hydrogen permeability. Interestingly, the styrene/VBC-grafted copolymer was found to be more mechanically resistant than the corresponding graft copolymer not containing the styrene component. For this reason, the copolymer g-VBC-5-co-Sty-16-Q with the best balance of mechanical, water uptake, and electrochemical properties was selected for a single-cell test in an AEM-WE.

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Tse, Mun F., A. J. Dias e H.-C. Wang. "Characterization and Physical Properties of New Isobutylene-Based Graft Copolymers". Rubber Chemistry and Technology 71, n. 4 (1 settembre 1998): 803–19. http://dx.doi.org/10.5254/1.3538506.

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Abstract A number of isobutylene-based graft copolymers with different compositions are compared to several commercial thermoplastic block copolymers, such as SIS, SBS and SEBS, in terms of morphology and viscoelasticity. The backbone of these graft copolymers is a terpolymer (BIMS) of isobutylene, p-methylstyrene and p-bromomethylstyrene, and the side chains are either polystyrene or poly(2,6-dimethyl-1,4-phenylene ether). Graft copolymer synthesis, statistics of graft formation, and stress-strain properties are described. Overall, these graft copolymers exhibit unique shear dependent viscosity effects, such as rapid thickening (quick setting) at low shear and lower viscosity (better processability) at high shear, compared to linear triblock copolymers. The rheological behavior of these graft copolymers could be a key advantage for high-shear calendering, extrusion, hot-melt spraying, and injection molding.

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Nguyen, Sophie. "Graft copolymers containing poly(3-hydroxyalkanoates) — A review on their synthesis, properties, and applications". Canadian Journal of Chemistry 86, n. 6 (1 giugno 2008): 570–78. http://dx.doi.org/10.1139/v08-044.

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The use of the poly(3-hydroxyalkanoates) in copolymer synthesis has received much interest, as the microbial polyester segments can bring interesting properties, such as biodegradability and biocompatibility. The synthesis, properties, and applications of graft copolymers containing poly(3-hydroxyalkanoates) as main chain or branches are reviewed here, with emphasis on the different preparation methods, which fit into the three main synthesis strategies of graft copolymers: “grafting onto”, “grafting from”, and “grafting through” or macromonomer methods.Key words: poly(3-hydroxyalkanoates), graft copolymer, synthesis, properties, applications.

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Pavlopoulou, Eleni, Kiriaki Chrissopoulou, Stergios Pispas, Nikos Hadjichristidis e Spiros H. Anastasiadis. "The Micellization of Well-Defined Single Graft Copolymers in Block Copolymer/Homopolymer Blends". Polymers 13, n. 5 (9 marzo 2021): 833. http://dx.doi.org/10.3390/polym13050833.

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A series of well-defined (polyisoprene)2(polystyrene), I2S, single graft copolymers with similar total molecular weights but different compositions, fPS, were blended with a low molecular weight polyisoprene homopolymer matrix at a constant concentration 2 wt%, and the micellar characteristics were studied by small-angle x-ray scattering. To investigate the effect of macromolecular architecture on the formation and characteristics of micelles, the results on the single graft copolymers were compared with those of the corresponding linear polystyrene-b-polyisoprene diblock copolymers, SI. The comparison reveals that the polystyrene core chains are more stretched in the case of graft copolymer micelles. Stretching turned out to be purely a result of the architecture due to the second polyisoprene block in the corona. The micellization of a (polystyrene)2(polyisoprene), S2I, graft copolymer was also studied, and the comparison with the results of the corresponding I2S and SI copolymers emphasizes the need for a critical core volume rather than a critical length of the core-forming block, in order to have stable micelles. Finally, the absence of micellization in the case of the I2S copolymer with the highest polystyrene volume fraction is discussed. For this sample, macrophase separation occurs, with polyisoprene cylinders formed in the copolymer-rich domains of the phase-separated blends.

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Nguyen, Thi Nhan, Hieu Nguyen Duy, Dung Tran Anh, Thuong Nghiem Thi, Thu Ha Nguyen, Nam Nguyen Van, Tung Tran Quang, Tung Nguyen Huy e Thuy Tran Thi. "Improvement of Thermal and Mechanical Properties of Vietnam Deproteinized Natural Rubber via Graft Copolymerization with Methyl Methacrylate". International Journal of Polymer Science 2020 (14 luglio 2020): 1–11. http://dx.doi.org/10.1155/2020/9037827.

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In this study, we investigated the improvement of the thermal and mechanical properties of Vietnam deproteinized natural rubber (DPNR) via graft copolymerization of methyl methacrylate (MMA). The graft copolymerization was achieved successfully in latex stage using tert-butyl hydroperoxide (TBHPO) and tetra-ethylenepentamine (TEPA) as radical initiators at 30°C. By grafting with various MMA feeds and initiator concentration of 6.6×10−5 mol/g-rubber, the highest grafting efficiency and conversion were achieved at MMA of 15 wt.% per kg of rubber, 68% and 90%, respectively. The structure of grafted copolymers was characterized by 1H NMR, FTIR-ATR, and GPC, and thermal properties were investigated through DSC and TGA measurements. These showed that graft copolymers were more stable and rigid than DPNR. Storage modulus (G′) of graft copolymer was found to double that of DPNR, which contributed to the formation of graft copolymer. After sulfur vulcanization, the mechanical properties of DPNR-graft-PMMA, such as tensile strength, tear strength, and hardness, were improved significantly. Curing behaviors of the graft copolymers were found to be remarkably better than virgin DPNR.

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Demina, Tatiana S., Maria G. Drozdova, Chantal Sevrin, Philippe Compère, Tatiana A. Akopova, Elena Markvicheva e Christian Grandfils. "Biodegradable Cell Microcarriers Based on Chitosan/Polyester Graft-Copolymers". Molecules 25, n. 8 (22 aprile 2020): 1949. http://dx.doi.org/10.3390/molecules25081949.

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Self-stabilizing biodegradable microcarriers were produced via an oil/water solvent evaporation technique using amphiphilic chitosan-g-polyester copolymers as a core material in oil phase without the addition of any emulsifier in aqueous phase. The total yield of the copolymer-based microparticles reached up to 79 wt. %, which is comparable to a yield achievable using traditional emulsifiers. The kinetics of microparticle self-stabilization, monitored during their process, were correlated to the migration of hydrophilic copolymer’s moieties to the oil/water interface. With a favorable surface/volume ratio and the presence of bioadhesive natural fragments anchored to their surface, the performance of these novel microcarriers has been highlighted by evaluating cell morphology and proliferation within a week of cell cultivation in vitro.

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Nikolic, Vladimir, Sava Velickovic, Dusan Antonovic e Aleksandar Popovic. "Biodegradation of starch–graft–polystyrene and starch–graft–poly(methacrylic acid) copolymers in model river water". Journal of the Serbian Chemical Society 78, n. 9 (2013): 1425–41. http://dx.doi.org/10.2298/jsc121216051n.

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In this paper the biodegradation study of grafted copolymers of polystyrene (PS) and corn starch and poly(methacrylic acid) and corn starch in model river water is described. These copolymers were obtained in the presence of different amine activators. The synthesized copolymers and products of degradation were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Biodegradation was monitored by mass decrease and number of microorganisms by Koch?s method. Biodegradation of both copolymers advanced with time, poly(methacrylic acid)-graft-starch copolymers completely degraded after 21 day, and polystyrene-graft-starch partially degraded (45.78-93.09 % of total mass) after 27 days. Differences in the degree of biodegradation are consequences of different structure of the samples, and there is a significant negative correlation between the share of polystyrene in copolymer and degree of biodegradation. The grafting degree of PS necessary to prevent biodegradation was 54 %. Based on experimental evidence, mechanisms of both biodegradation processes are proposed, and influence of degree of starch and synthetic component of copolymers on degradation were established.

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8

Song, Lixin, Qian Zhang, Yongsheng Hao, Yongchao Li, Weihan Chi, Fei Cong, Ying Shi e Li-Zhi Liu. "Effect of Different Comonomers Added to Graft Copolymers on the Properties of PLA/PPC/PLA-g-GMA Blends". Polymers 14, n. 19 (29 settembre 2022): 4088. http://dx.doi.org/10.3390/polym14194088.

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The melt-free radical grafting of glycidyl methacrylate (GMA) onto poly (lactic acid) (PLA) with styrene (St), α-methylstyrene (AMS), and epoxy resin (EP) as comonomers in a twin-screw extruder was used to prepare PLA-g-GMA graft copolymers. The prepared graft copolymers were then used as compatibilizers to prepare PLA/PPC/PLA-g-GMA blends by melt blending with PLA and polypropylene carbonate (PPC), respectively. The effects of different comonomers in the PLA-g-GMA graft copolymers on the thermal, rheological, optical, and mechanical properties and microstructure of the blends were studied. It was found that the grafting degree of PLA-g-GMA graft copolymers was increased to varying degrees after the introduction of comonomers in the PLA-g-GMA grafting reaction system. When St was used as the comonomer, the grafting degree of the PLA-g-GMA graft copolymer increased most significantly, from 0.8 to 1.6 phr. St as a comonomer also most improved the compatibility between PLA and PPC, and the haze of the blends was reduced while maintaining high transmittance. In addition, the PLA-g-GMA graft copolymer with the introduction of St as a comonomer significantly improved the impact toughness of the blends, while the thermal stability and tensile strength of the blends remained largely unchanged.

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Ashish Chauhan e Balbir Kaith. "Exploring the Diversification in Grafted Copolymer". International Journal of Fundamental and Applied Sciences (IJFAS) 1, n. 2 (30 giugno 2012): 14–19. http://dx.doi.org/10.59415/ijfas.v1i2.24.

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The paper deals with optimization of the reaction parameters, graft copolymerization, characterizationand evaluation of the transformations in Roselle stem fiber on graft copolymerization with vinyl monomer, using cericammonium nitrate nitric acid initiator system. Methods: Different reaction parameters such as temperature, time, initiatorconcentration, monomer concentration and pH were optimized to get the maximum graft yield. The graft copolymer thusformed were characterized by advanced techniques. Results: The physico-chemico-thermal resistance, moisture absorbance,swelling behavior of graft copolymers and the dye uptake behavior were studied and found to have improved. Conclusion:Hence, this first report of novel graft copolymers is to help towards various applications.

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Liu, Yun-Hai, Xiao-Hong Cao, Dao-Feng Peng e Wen-Yuan Xu. "Polycationic graft copolymers of poly(N-vinylpyrrolidone) as non-viral vectors for gene transfection". Open Chemistry 7, n. 3 (1 settembre 2009): 532–41. http://dx.doi.org/10.2478/s11532-009-0045-8.

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AbstractNovel graft copolymers of 2-(dimethylamino)ethyl methacrylate (DMAEMA) with N-vinylpyrrolidone (NVP) were designed and synthesized by the free radical copolymerization of DMAEMA with precursor polymers of vinyl-functionalized poly(N-vinylpyrrolidone) (PVP). The ability of the PVP- grafted copolymers to bind and condense DNA was confirmed by ethidium bromide displacement assay, agarose gel electrophoresis and transmission electron microscopy. The presence of PVP in the copolymers had a favorable effect on the biophysical properties of polymer/DNA complexes. Colloidal stable complexes obtained from the copolymer systems, were shown to be separate, uniformly spherical nanoparticles by transmission electron microscopy. The approximate diameter of the complexes was 150–200 nm, as determined by dynamic light scattering studies. These results confirm an important role played by the PVP grafts in producing compact stable DNA complexes. The ζ-potential measurements revealed that the incorporation of the PVP grafts reduced the positive surface charge of polymer/DNA complexes. The cytotoxicity of the copolymers decreased with an increasing fraction of PVP. Furthermore, in vitro transfection experiments with these copolymers showed improved ability of transfection in cell culture, demonstrating an important role for PVP grafts in enhancement of the transfection efficiency.

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Kaliva, Maria, Anthie Georgopoulou, Dimitrios A. Dragatogiannis, Costas A. Charitidis, Maria Chatzinikolaidou e Maria Vamvakaki. "Biodegradable Chitosan-graft-Poly(l-lactide) Copolymers For Bone Tissue Engineering". Polymers 12, n. 2 (4 febbraio 2020): 316. http://dx.doi.org/10.3390/polym12020316.

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The design and synthesis of new biomaterials with adjustable physicochemical and biological properties for tissue engineering applications have attracted great interest. In this work, chitosan-graft-poly(l-lactide) (CS-g-PLLA) copolymers were prepared by chemically binding poly(l-lactide) (PLLA) chains along chitosan (CS) via the “grafting to” approach to obtain hybrid biomaterials that present enhanced mechanical stability, due to the presence of PLLA, and high bioactivity, conferred by CS. Two graft copolymers were prepared, CS-g-PLLA(80/20) and CS-g-PLLA(50/50), containing 82 wt % and 55 wt % CS, respectively. Degradation studies of compressed discs of the copolymers showed that the degradation rate increased with the CS content of the copolymer. Nanomechanical studies in the dry state indicated that the copolymer with the higher CS content had larger Young modulus, reduced modulus and hardness values, whereas the moduli and hardness decreased rapidly following immersion of the copolymer discs in alpha-MEM cell culture medium for 24 h. Finally, the bioactivity of the hybrid copolymers was evaluated in the adhesion and growth of MC3T3-E1 pre-osteoblastic cells. In vitro studies showed that MC3T3-E1 cells exhibited strong adhesion on both CS-g-PLLA graft copolymer films from the first day in cell culture, whereas the copolymer with the higher PLLA content, CS-g-PLLA(50/50), supported higher cell growth.

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Che, Ning, Saina Yang, Hongliang Kang, Ruigang Liu, Zhuang Li, Zhijing Liu, Pingping Li, Xiaozhong Qu e Yong Huang. "Synthesis and properties of CO2-switchable Dex-g-PAHMA copolymers". Polym. Chem. 5, n. 24 (2014): 7109–20. http://dx.doi.org/10.1039/c4py00987h.

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CO₂-switchable Dex-g-PAHMA copolymers were synthesized and characterized. The properties of the graft copolymers and the cytotoxicity and cellular uptake of DOX-loaded Dex-g-PAHMA copolymer micelles were investigated.

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Jarosz, Tomasz, Karolina Gebka e Agnieszka Stolarczyk. "Recent Advances in Conjugated Graft Copolymers: Approaches and Applications". Molecules 24, n. 16 (20 agosto 2019): 3019. http://dx.doi.org/10.3390/molecules24163019.

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The main goal of this mini review is to summarise the most recent progress in the field of conjugated graft copolymers featuring conjugation across the main chain, across side chains or across both. The main approaches to the synthesis of conjugated graft copolymers are highlighted, and the various trends in the development of new copolymer materials and the intended directions of their applications are explored.

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Smirnov, Anton K., e Anna B. Shipovskaya. "Synthesis and properties of grafted copolymers of xanthan and glucomannan with acrylic monomers". Izvestiya of Saratov University. Chemistry. Biology. Ecology 23, n. 2 (21 giugno 2023): 185–96. http://dx.doi.org/10.18500/1816-9775-2023-23-2-185-196.

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Graft copolymers of polysaccharides with acrylic monomers combine biodegradability, biocompatibility, the environmental friendliness of natural polymers and the increased thermal stability, chemical and mechanical resistance of synthetic polymers. This paper describes our search and analysis of the literature in English for 2002–2022 devoted to the graft polymerization of acrylamide, acrylic acid and 2-acrylamido- 2-methylpropanesulfonic acid onto xanthan and glucomannan macromolecular chains. It has been found that the synthesis of grafted copolymer chains proceeds by a radical polymerization mechanism using thermal homolytic decomposition of the initiator or microwave irradiation, or radiation initiation and frontal polymerization in some cases. Depending on the method of the reaction, the synthesis time of a graft copolymer varies from several minutes to several hours. The influence of the synthesis conditions and parameters on the monomer conversion, structure and properties of the resulting polymer has been considered. It has been found that decreasing the polysaccharide/monomer ratio and increasing the initiator concentration raise the efficiency and degree of grafting. Several methods for characterization of graft copolymers are discussed, including: IR spectroscopy to analyze the chemical structure of a sample, scanning electron microscopy to characterize structure, supramolecular ordering and porosity, differential thermal analysis to evaluate thermal effects and thermal stability. The effect of the synthesis conditions and the pH of the sorption medium on the water absorption and sorption capacity of this class of graft copolymers are discussed. The broad potential of graft copolymers for repeated cycles of absorption and release of liquid medium without loss of functional properties has been found. This opens prospects for the use of graft copolymers of xanthan and glucomannan with acrylic monomers as materials for water purification from metal ions and cationic dyes, targeted delivery and prolonged action of drugs and wound coatings for wound treatment.

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Wu, Xiu Li, Pi Xin Wang e Ya Cui Guo. "Preparation and Characterization of Graft Copolymer of Acryloyloxyethyl-Trimethylammonium Chloride and Starch". Advanced Materials Research 634-638 (gennaio 2013): 1977–80. http://dx.doi.org/10.4028/www.scientific.net/amr.634-638.1977.

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Using ammonium persulfate (APS) as the initiator, a series of cationic starch— acyrloxyethyl-trimethylammonium chloride (DAC) graft copolymers containing quaternary ammonium groups were prepared in aqueous solution. The results showed that the cationic graft copolymer of high cationic degree (DC) could be obtained in this reaction system. The maximum DC of 53.68% was achieved with ASP/starch mass percentage 1.0%, m(DAC):m(starch) = 2.5,at 50°C and reaction time 8h. Structures of the graft copolymers were characterized by FTIR, scanning electron microscope (SEM) and thermo-gravimetric/differential thermal analyze (TG-DTA).

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Tarabukina, Elena, Emil Fatullaev, Anna Krasova, Mikhail Kurlykin, Andrey Tenkovtsev, Sergei S. Sheiko e Alexander Filippov. "Synthesis, Structure, Hydrodynamics and Thermoresponsiveness of Graft Copolymer with Aromatic Polyester Backbone at Poly(2-isopropyl-2-oxazoline) Side Chains". Polymers 12, n. 11 (10 novembre 2020): 2643. http://dx.doi.org/10.3390/polym12112643.

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New thermoresponsive graft copolymers with an aromatic polyester backbone and poly(2-isopropyl-2-oxazoline) (PiPrOx) side chains are synthesized and characterized by NMR and GPC. The grafting density of side chains is 0.49. The molar masses of the graft-copolymer, its backbone, side chains, and the modeling poly-2-isopropyl-2-oxaziline are 74,000, 19,000, 4300, and 16,600 g·mol−1, respectively. Their conformational properties in nitropropane as well as thermoresponsiveness in aqueous solutions are studied and compared with that of free side chains, i.e., linear PiPrOx with a hydrophobic terminal group. In nitropropane, the graft-copolymer adopts conformation of a 13-arm star with a core of a collapsed main chain and a PiPrOx corona. Similarly, a linear PiPrOx chain protects its bulky terminal group by wrapping around it in a selective solvent. In aqueous solutions at low temperatures, graft copolymers form aggregates due to interaction of hydrophobic backbones, which contrasts to molecular solutions of the model linear PiPrOx. The lower critical solution temperature (LCST) for the graft copolymer is around 20 °C. The phase separation temperatures of the copolymer solution were lower than that of the linear chain counterpart, decreasing with concentration for both polymers.

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Jeon, Oju, Su Jin Song, Min Hyung Lee, Sang Woo Seo, Cha Yong Choi e Byoung Soo Kim. "Synthesis and Characterization of Polyethylenimine-Graft-Poly(L-Lactide-Co-Glycolide) Block Copolymers for Gene Delivery". Key Engineering Materials 342-343 (luglio 2007): 521–24. http://dx.doi.org/10.4028/www.scientific.net/kem.342-343.521.

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Polyethylenimine-graft-poly(L-lactide-co-glycolide) (PEI-g-PLGA) block copolymers were prepared by a ring-opening polymerization of L-lactide and glycolide using PEI as a macroinitiator and stannous octoate as a catalyst in dimethylformamide at 100 °C. The molecular structure of the block copolymers was evaluated with 1H-NMR, and the molecular weight of the block copolymers was determined with gel permeation chromatography. The thermal properties were investigated using differential scanning calorimetery and thermogravimetric analysis. The zetapotential of the pDNA/copolymer complexes was evaluated with dynamic laser light scattering. Cytotoxicity and gene transfection efficiency of PEI-g-PLGA were tested in vitro using human embryonic kidney 293 cell culture. The pDNA/copolymer complexes (N/P = 10) showed a lower zeta-potential than pDNA/PEI25kDa complex, suggesting the lower toxicity of the pDNA/copolymer complexes. The copolymer composition was found to significantly affect the gene transfection efficiency of the pDNA/copolymer complexes. The copolymers with lower contents of PLGA showed higher gene transfection efficiency. These results indicate that these block copolymers are promising candidates for gene delivery vehicles, featuring good biocompatibility, potential biodegradability, and relatively high gene transfection efficiency.

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Cheaburu-Yilmaz, Catalina, Catalina Lupuşoru e Cornelia Vasile. "New Alginate/PNIPAAm Matrices for Drug Delivery". Polymers 11, n. 2 (20 febbraio 2019): 366. http://dx.doi.org/10.3390/polym11020366.

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This paper deals with a comparative study on the interpolymeric complexes of alginate poly(N-isopropyl acryl amide (PNIPAAm) and corresponding graft copolymers with various compositions in respect to their toxicity, biocompatibility and in vitro and in vivo release of theophylline (THP). Loading of the various matrices with theophylline and characterization of loaded matrices was studied by near infrared spectroscopy–chemical imaging (NIR–CI) analysis, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). It was appreciated that THP loading is higher than 40% and the drug is relatively homogeneous distributed within all matrices because of some specific interactions between components of the system. All samples have been found to be non-toxic and biocompatible. It was established that graft copolymers having a good stability show a better drug carrier ability, a higher THP loading, a prolonged release (longer release duration for graft copolymers of 235.4–302.3 min than that for IPC 72/28 of 77.6 min, which means approximately four times slower release from the graft copolymer-based matrices than from the interpolymeric complex) and a good bioavailability. The highest values for THP loading (45%), prolonged release (302.3 min) and bioavailability (175%) were obtained for graft copolymer AgA-g-PNIPAAm 68. The drug release mechanism varies with composition and architecture of the matrix.

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Tarabukina, Elena, Emil Fatullaev, Anna Krasova, Maria Sokolova, Mikhail Kurlykin, Igor Neelov, Andrey Tenkovtsev e Alexander Filippov. "Thermoresponsive Molecular Brushes with a Rigid-Chain Aromatic Polyester Backbone and Poly-2-alkyl-2-oxazoline Side Chains". International Journal of Molecular Sciences 22, n. 22 (12 novembre 2021): 12265. http://dx.doi.org/10.3390/ijms222212265.

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A new polycondensation aromatic rigid-chain polyester macroinitiator was synthesized and used to graft linear poly-2-ethyl-2-oxazoline as well as poly-2-isopropyl-2-oxazoline by cationic polymerization. The prepared copolymers and the macroinitiator were characterized by NMR, GPC, AFM, turbidimetry, static, and dynamic light scattering. The molar masses of the polyester main chain and the grafted copolymers with poly-2-ethyl-2-oxazoline and poly-2-isopropyl-2-oxazoline side chains were 26,500, 208,000, and 67,900, respectively. The molar masses of the side chains of poly-2-ethyl-2-oxazoline and poly-2-isopropyl-2-oxazoline and their grafting densities were 7400 and 3400 and 0.53 and 0.27, respectively. In chloroform, the copolymers conformation can be considered as a cylinder wormlike chain, the diameter of which depends on the side chain length. In water at low temperatures, the macromolecules of the poly-2-ethyl-2-oxazoline copolymer assume a wormlike conformation because their backbones are well shielded by side chains, whereas the copolymer with short side chains and low grafting density strongly aggregates, which was visualized by AFM. The phase separation temperatures of the copolymers were lower than those of linear analogs of the side chains and decreased with the concentration for both samples. The LCST were estimated to be around 45 °C for the poly-2-ethyl-2-oxazoline graft copolymer, and below 20 °C for the poly-2-isopropyl-2-oxazoline graft copolymer.

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Boustta, Mahfoud, e Michel Vert. "Hyaluronic Acid-Poly(N-acryloyl glycinamide) Copolymers as Sources of Degradable Thermoresponsive Hydrogels for Therapy". Gels 6, n. 4 (23 novembre 2020): 42. http://dx.doi.org/10.3390/gels6040042.

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One-pot free-radical polymerization of N-acryloyl glycinamide in the presence of hyaluronic acid as transfer-termination agent led to new copolymers in high yields without any chemical activation of hyaluronic acid before. All the copolymers formed thermoresponsive hydrogels of the Upper Critical Solution Temperature-type in aqueous media. Gel properties and the temperature of the reversible gel ↔ sol transition depended on feed composition and copolymer concentration. Comparison with mixtures of hyaluronic acid-poly(N-acryloyl glycinamide) failed in showing the expected formation of graft copolymers conclusively because poly(N-acryloyl glycinamide) homopolymers are also thermoresponsive. Grafting and formation of comb-like copolymers were proved after degradation of inter-graft hyaluronic acid segments by hyaluronidase. Enzymatic degradation yielded poly(N-acryloyl glycinamide) with sugar residues end groups as shown by NMR. In agreement with the radical transfer mechanism, the molar mass of these released poly(N-acryloyl glycinamide) grafts depended on the feed composition. The higher the proportion of hyaluronic acid in the feed, the lower the molar mass of poly(N-acryloyl glycinamide) grafts was. Whether molar mass can be made low enough to allow kidney filtration remains to be proved in vivo. Last but not least, Prednisolone was used as model drug to show the ability of the new enzymatically degradable hydrogels to sustain progressive delivery for rather long periods of time in vitro.

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Kuznetsova, Yulia, Ksenya Gushchina, Karina Sustaeva, Alexander Mitin, Marfa Egorikhina, Victoria Chasova e Lyudmila Semenycheva. "Grafting of Methyl Methacrylate onto Gelatin Initiated by Tri-Butylborane—2,5-Di-Tert-Butyl-p-Benzoquinone System". Polymers 14, n. 16 (12 agosto 2022): 3290. http://dx.doi.org/10.3390/polym14163290.

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Graft gelatin and poly(methyl methacrylate) copolymers were synthesized in the presence of the tributylborane—2,5-di-tert-butyl-p-benzoquinone (2,5-DTBQ) system. The molecular weight parameters and morphology of the polymer indicate that it has a cross-linked structure. Obtained data confirm the simultaneous formation of a copolymer in two ways: “grafting from” and “grafting to”. It leads to the cross-linked structure of a copolymer. This structure was not obtained for copolymers synthesized in the presence of other initiating systems: azobisisobutyronitrile; tributylborane; azobisisobutyronitrile and tributylborane; azobisisobutyronitrile, tributylborane, and 2,5-di-tert-butyl-p-benzoquinone. In these cases, the possibility of the formation of the copolymer, simultaneously in two ways, was excluded. Graft gelatin and poly(methyl methacrylate) copolymers synthesized in the presence of the tributylborane—2,5-di-tert-butyl-p-benzoquinone system are promising in terms of their use in scaffold technologies due to the three-dimensional mesh structure, providing a high regenerative potential of materials.

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Sorokin, Andrey V., Svetlana S. Olshannikova, Maria S. Lavlinskaya, Marina G. Holyavka, Dzhigangir A. Faizullin, Yuriy F. Zuev e Valeriy G. Artukhov. "Chitosan Graft Copolymers with N-Vinylimidazole as Promising Matrices for Immobilization of Bromelain, Ficin, and Papain". Polymers 14, n. 11 (3 giugno 2022): 2279. http://dx.doi.org/10.3390/polym14112279.

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Abstract (sommario):

This work aims to synthesize graft copolymers of chitosan and N-vinylimidazole (VI) with different compositions to be used as matrices for the immobilization of cysteine proteases—bromelain, ficin, and papain. The copolymers are synthesized by free radical solution copolymerization with a potassium persulfate-sodium metabisulfite blend initiator. The copolymers have a relatively high frequency of grafting and yields. All the synthesized graft copolymers are water-soluble, and their solutions are characterized by DLS and laser Doppler microelectrophoresis. The copolymers are self-assembled in aqueous solutions, and they have a cationic nature and pH-sensitivity correlating to the VI content. The FTIR data demonstrate that synthesized graft copolymers conjugate cysteine proteases. The synthesized copolymer adsorbs more enzyme macromolecules compared to non-modified chitosan with the same molecular weight. The proteolytic activity of the immobilized enzymes is increased up to 100% compared to native ones. The immobilized ficin retains up to 97% of the initial activity after a one-day incubation, the immobilized bromelain retains 69% of activity after a 3-day incubation, and the immobilized papain retains 57% of the initial activity after a 7-day incubation. Therefore, the synthesized copolymers can be used as matrices for the immobilization of bromelain, ficin, and papain.

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23

Storti, Gia, Giulia Romano, Kristen Gilmore, Nicholas Sadowski, Andrii Tiiara, Igor Luzinov e Alexander Sidorenko. "Permeability of Skin-Mimicking Cell Coatings by Polymers of Complex Architecture Based on Polyoxazolines". Coatings 13, n. 6 (29 maggio 2023): 1007. http://dx.doi.org/10.3390/coatings13061007.

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Abstract (sommario):

In the scope of drug delivery, the transdermal route is desirable because it provides attainable therapeutic concentrations and has minimal systemic side effects. To make the skin a feasible route for the delivery of therapeutic agents, the biggest challenge is overcoming its natural coating. In this paper, we investigate the effect of the architectures (homopolymer vs. block copolymer vs. hybrid block–graft copolymer) of several amphiphilic polymeric derivatives of poly(2-oxazoline) on skin permeability. The block copolymers are composed of a hydrophobic poly(2-oxazoline) block and a hydrophilic PEG block. The hybrid block–graft copolymers are obtained by grafting hydrophobic side chains of polycaprolactone to a poly(2-oxazoline) backbone. We used the commercially available EpiDerm™ by MatTek, composed of human epidermal cells, as a model of human skin. Two parameters of skin permeation are reported: penetration rate and lag time. We hypothesize that the skin permeation characteristics correlate with the critical micelle concentration and particle size of the studied polymers, while both parameters are a function of the complex architectures of the presented macromolecular constructs. While homopolymer poly(2-oxazolines) show the least permeation, the block copolymers demonstrate partial permeation. The hybrid block–graft copolymers exhibited full penetration through the model skin samples.

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24

Maruyama, Atsushi, Long Liang Wu, Naohiko Shimada e Arihiro Kano. "Kinetic Effect of Cationic Comb-Type Copolymers on DNA Hybridization". Advanced Materials Research 47-50 (giugno 2008): 1355–58. http://dx.doi.org/10.4028/www.scientific.net/amr.47-50.1355.

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Abstract (sommario):

We have been interested in the soluble interpolyelectrolyte complexes (IPEC) between DNA and the cationic comb-type copolymers, poly(L-lysine)-graft-dextran (PLL-g-Dex), consisting of a polylysine backbone and abundant hydrophilic graft chains of dextran as a model of nucleic acid-binding proteins. In this paper, we described the kinetic effect of the copolymers on the DNA hybridization. We found that the cationic copolymer at nano molar concentrations in cationic groups accelerated DNA duplex formation by two orders under physiologically relevant conditions.

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25

Panzarini, Luz Consuelo Gonzalez Alonso, Andreia de Araújo Morandim-Giannetti e Selma Matheus Loureiro Guedes. "Manufacture of non-thrombogenic polymer surfaces by gamma irradiation to induce simultaneous grafting and heparinization of thin PVC films". Journal of Bioactive and Compatible Polymers 36, n. 4 (luglio 2021): 283–95. http://dx.doi.org/10.1177/08839115211030634.

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Abstract (sommario):

Investigations regarding alternative methods for producing polymeric materials with hydrophilic properties have increased considerably. In this context, polymeric biomaterials with hemocompatible surface properties have been successfully obtained by grafting hydrophilic monomers onto commercial polymer films by simultaneous irradiation processes. In this study, simultaneous irradiation and grafting were used to produce a copolymer PVC-co-DMAEMA-co-heparin with hemocompatible surface properties. Characterization by FTIR of the graft copolymer indicates that the increase in monomer grafting levels inhibits the bonding sites to heparin. FTIR-PAS analyses of the graft copolymers showed that the highest graft levels were obtained for the irradiated samples containing 45% of monomer. Heparin, however, could only be detected in the irradiated samples containing 30% of DMAEMA. The analysis of the micrographs, on the other hand, showed that increasing the monomer concentration enhances surface roughness of the graft copolymers. Roughness however decreased with heparin addition. It was possible to verify that an excess of surface roughness of the graft copolymers inhibits anticoagulant properties of heparin, triggering thrombus formation. Platelet adhesion, on its turn, was not significantly affected by the presence of heparin when PVC-co-DMAEMA and PVC-co-DMAEMA-co-heparin, obtained from the systems containing 45% of monomer, are compared. The addition of heparin in the systems containing 30% of DMAEMA resulted in fewer thrombogenic surfaces.

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26

Obshitser, Arthur S., Telman A. Bayburdov e Sergei L. Shmakov. "Free-radical graft copolymerization acrylamide, 2-sodium 2-acrylamido-2-methylpropane sulfonic onto chitosan". Izvestiya of Saratov University. Chemistry. Biology. Ecology 23, n. 1 (21 marzo 2023): 18–27. http://dx.doi.org/10.18500/1816-9775-2023-23-1-18-27.

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Abstract (sommario):

The method presents obtaining hydrosoluble graft copolymer of complicated structure based on сhitosan, acrylamide (AM), sodium 2-acrylamido-2-methylpropane sulfonic (АМPS-Na) in order to obtain flocсulant which is resistant to salt of transition metals and heat temperature, and in order to use it as a reagent for oil production processes. The obvious advantages of this copolymer can be attributed to its biodegradation due to inclusion of a biopolymer into the composition of the copolymer, which is important for the preservation of ecology, and efficiency of its synthetic analogues. The graft copolymerization acrylamide and sodium 2-acrylamido-2-methylpropane sulfonic onto active sites of chitosan has been performed under condition of high concentration monomers in nitrogen atmosphere using combined initiator system of complex composition under the following order monomers [АА]>[АМПС-Na]. Kinetic study of graft copolymerization has been carried out using thermometry methods. Attempts have been made to describe mathematically the reaction of graft monomers АM and АМPS-Na onto chitosan. The IR spectra analysis of copolymers has been carried out. The study of reaction rate and molecular characteristics of synthesized copolymers has been conducted under changing concentration of chitosan, monomers, ratio components of the initiator system and reaction temperature during synthesis. It has been determined that the averaged energy activation of copolymerization reaction was in the range of reaction temperature 10–25°С. Molecular composition and proposed structure of the grafted copolymers have been determined by the results of viscosity and sedimentation analysis. The results of this study allow to obtain grafted copolymers with specified properties and structure to use them in such areas as sewage and industrial water treatment and mineral industry.

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27

Xin, Ting-Ting, Tongqi Yuan, Shu Xiao e Jing He. "Synthesis of cellulose-graft-poly(methyl methacrylate) via homogeneous ATRP". BioResources 6, n. 3 (20 giugno 2011): 2941–53. http://dx.doi.org/10.15376/biores.6.3.2941-2953.

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Abstract (sommario):

Cellulose-graft-poly(methylmethacrylate) (cellulose-g-PMMA) copolymers were prepared by homogeneous atom transfer radical polymerization (ATRP) under mild conditions, in an attempt to develop an efficient way to modify the surface of cellulose. A cellulose macro-initiator was successfully synthesized by direct homogeneous acylation of cellulose with 2-bromopropionyl bromide in a room temperature ionic liquid (RTIL), 1-allyl-3-methylimidazolium chloride ([AMIM]Cl). Copolymers were obtained via ATRP of methyl methacrylate (MMA) with CuBr/penta-methyldiethylenetriamine (PMDETA) as catalyst and N,N-dimethyl-formamide (DMF) as solvent without homopolymer byproduct. The grafting copolymers were characterized by 1H-NMR, 13C-NMR, and FTIR. The grafted PMMA chain was obtained by the hydrolysis of the cellulose backbone and analyzed by GPC and TGA measurements. In addition, the assemblies or aggregates formed by cellulose-g-PMMA copolymers were studied by means of TEM and AFM. The results indicated that the graft polymerization occurred from the cellulose backbone and the obtained copolymers had grafted polymer chains with well-controlled molecular weight and polydispersity; the cellulose graft copolymer in solution could aggregate and self-assemble into sphere-like structures.

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28

Zhu, Jiang, e Xiu Li Wang. "Green Synthesis of Poly(ρ-Dioxanone)-Modified Cellulose by Lipase-Catalyzed Ring-Opening Polymerization in Ionic Liquid". Advanced Materials Research 581-582 (ottobre 2012): 100–103. http://dx.doi.org/10.4028/www.scientific.net/amr.581-582.100.

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Abstract (sommario):

A new cellulose graft copolymer was synthesized by the lipase-catalyzed ring-opening polymerization of ρ-dioxanone (PDO) onto cellulose in 1-N-butyl-3-methylimidazolium chloride ([Bmim]Cl). The structure of the copolymer was characterized by FT-IR and 1H-NMR. The obtained copolymers exhibited the different thermal stability by TGA after the graft copolymerization. The reaction media applied can be easily recycled and reused.

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29

Stejskal, Jaroslav, Pavel Kratochvil e Aubrey D. Jenkins. "Graft copolymer statistics. 2. Application to graft copolymers prepared from macromonomers". Macromolecules 20, n. 1 (gennaio 1987): 181–85. http://dx.doi.org/10.1021/ma00167a031.

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30

Negim, El-Sayed, A. M. Konysbay, G. Irmukhametova e S. N. Kalugin. "Synthesis and characterization of polypropylene glycol-graft-styrene". Kompleksnoe Ispolʹzovanie Mineralʹnogo syrʹâ/Complex Use of Mineral Resources/Mineraldik Shikisattardy Keshendi Paidalanu 318, n. 3 (12 settembre 2021): 5–11. http://dx.doi.org/10.31643/2021/6445.23.

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Abstract (sommario):

Grafting polymerization based on polypropylene glycol (PPG) and styrene (St) was synthesized with different composition of styrene using the free radical technique in the presence of potassium persulphate as an initiator. The grafted copolymers (PPG-g-St) used different styrene composition (65/15, 65/25, 65/35), respectively. The grafted copolymers were investigated through FTIR (Fourier-transform spectroscopy), Differential scanning calorimeter and thermogravimetric analyzer. FTIR showed new peaks at 1450 cm-1 and 1135 cm-1 due to the grafting process of St on PPG. Thermal stability of grafted copolymer increases by increasing the ratio of styrene, while Tg decreases by increasing the ratio of styrene.

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31

Lee, Young Hee, Jung Soo Kim e Han Do Kim. "A Study of Biodegradable Superabsorbent Materials Based on Acrylonitrile Grafted Sodium Alginate". Key Engineering Materials 277-279 (gennaio 2005): 450–54. http://dx.doi.org/10.4028/www.scientific.net/kem.277-279.450.

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Abstract (sommario):

Biodegradable superabsorbents, hydrolyzed AN(acrylonitrile)-grafted-SA(sodium alginate) copolymers were prepared in this study by graft copolymerization of acrylonitrile on sodium alginate and the subsequent hydrolysis of the resulting grafted copolymer. The absorbency was found to significantly depend on the % add-on, graft copolymerization conditions and hydrolysis conditions. The optimum condition for graft copolymerization to obtain the maximum % add-on (64.5%) was 4g SA, 12g AN, and 8.42g H2O2 in 100ml water at 70 oC for 10hr., respectively. The optimum hydrolysis conditions for the graft copolymer (64.5 % add-on) to reach the maximum water absorbency (2518g/g), saline absorbency (1558g/g), and WRV (288g/g) is 1g graft copolymer in 10 ml aqueous NaOH (1.0N) at 110 oC for 1 hr. Furthermore, this hydrolyzed AN-graft-SA showed a good biodegradability in enzymatic hydrolysis tests when compared with commercial superabsorbent materials.

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32

Tezuka, Yasuyuki, Akitoshi Araki e Tomoo Shiomi. "Surface formation and environmental responses on polyurethane-polystyrene graft copolymers". High Performance Polymers 7, n. 3 (giugno 1995): 283–91. http://dx.doi.org/10.1088/0954-0083/7/3/005.

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Abstract (sommario):

The surfaces of polyurethane (PU)-polystyrene (PS) graft copolymers having a defined content of uniform-size polystyrene graft segments were studied in both dry and wet states. XPS inspection of PU-PS graft copolymer film samples indicated the enrichment of the PS component at the surface in the dry state. The sample films were then immersed in water, and the environmental response at the surface was examined by means of a contact angle measurement using a CCI4 in water technique. The contact angle underwent a slow, but measurable change from one near to that of the PS homopolymer toward that of the PU homopolymer within a 3 h period for the graft copolymer samples annealed at 80 C. On the other hand, the contact angle remained close to that of the PU homopolymer within a 3 h period for samples annealed at 120'C.

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33

ADELI, MOHSEN, REZA SEPAHVAND, ALI BAHARI e BANDAR ASTINCHAP. "CARBON NANOTUBE-GRAFT-BLOCK COPOLYMERS CONTAINING SILVER NANOPARTICLES". International Journal of Nanoscience 08, n. 06 (dicembre 2009): 533–41. http://dx.doi.org/10.1142/s0219581x09006365.

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Abstract (sommario):

Polycaprolactone-polylactide block copolymers (PCL-block-PLA) were grafted onto filled multi-wall carbon nanotubes (MWCNT) successfully. In this synthesis, MWCNTs were opened and functionalized, and then they were filled by silver nanoparticles. The filled MWCNT were used as macroinitiator for ring opening polymerization of ε-caprolactone and L-lactide. Then the end hydroxyl functional groups of MWCNT-graft-PCL or MWCNT-graft-PLA were used as initiator for ring opening polymerization of lactide and ε-caprolactone and MWCNT-graft-PCL-block-PLA or MWCNT-graft-PLA-block-PCL were obtained, respectively. Length of grafted copolymer chains onto the MWCNT was controlled using CNT/monomer ratio. Nanocomposites' properties depend on the length of polymer blocks strongly. Structure of nanocomposites was evaluated by TEM and spectroscopy methods.

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34

Kuznetsova, Yulia L., Ksenya S. Gushchina, Karina S. Lobanova, Victoria O. Chasova, Marfa N. Egorikhina, Alexandra O. Grigoreva, Yulia B. Malysheva et al. "Scaffold Chemical Model Based on Collagen—Methyl Methacrylate Graft Copolymers". Polymers 15, n. 12 (8 giugno 2023): 2618. http://dx.doi.org/10.3390/polym15122618.

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Abstract (sommario):

Polymerization of methyl methacrylate (MMA) in aqueous collagen (Col) dispersion was studied in the presence of tributylborane (TBB) and p-quinone: 2,5-di-tert-butyl-p-benzoquinone (2,5-DTBQ), p-benzoquinone (BQ), duroquinone (DQ), and p-naphthoquinone (NQ). It was found that this system leads to the formation of a grafted cross-linked copolymer. The inhibitory effect of p-quinone determines the amount of unreacted monomer, homopolymer, and percentage of grafted poly(methyl methacrylate) (PMMA). The synthesis combines two approaches to form a grafted copolymer with a cross-linked structure—“grafting to” and “grafting from”. The resulting products exhibit biodegradation under the action of enzymes, do not have toxicity, and demonstrate a stimulating effect on cell growth. At the same time, the denaturation of collagen occurring at elevated temperatures does not impair the characteristics of copolymers. These results allow us to present the research as a scaffold chemical model. Comparison of the properties of the obtained copolymers helps to determine the optimal method for the synthesis of scaffold precursors—synthesis of a collagen and poly(methyl methacrylate) copolymer at 60 °C in a 1% acetic acid dispersion of fish collagen with a mass ratio of the components collagen:MMA:TBB:2,5-DTBQ equal to 1:1:0.015:0.25.

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35

Carrero, Maria G., James J. Posada e Marcos A. Sabino. "Intelligent copolymers based on poly (N-isopropylacrylamide) PNIPAm with potential use in biomedical applications. Part i: PNIPAm functionalization with 3-butenoic acid and piperazine". International Journal of Advances in Medical Biotechnology - IJAMB 1, n. 1 (14 marzo 2018): 13. http://dx.doi.org/10.25061/2595-3931/ijamb/2018.v1i1.9.

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Abstract (sommario):

The synthesis and characterization of the thermosensitive copolymers based on Poly (N-Isopropylacrylamide) (PNIPAm) and 3-butenoic acid and functionalized with piperazine was carried out. The free radical polymerization of the PNIPA copolymer with 3-butenoic acid was performed under microwave radiation. After obtaining this copolymer, the carboxyl groups present in the copolymer chain were activated with 1-ethyl- (3-3-dimethylaminopropyl) carbodiimide in the presence of N-hydroxysuccinimide, improving its reactivity to incorporate the piperazine through its amino group. The characterization consisted: differential scanning calorimetric and ultraviolet-visible spectrophotometry to determine the LCST phase transition temperature, ranging from (30-35)°C. Structurally it was analyzed by infrared spectroscopy. A morphological analysis was performed using scanning electron microscopy, after simulating an injectable process, with the objective to observe internally the porosity and interconnectivity. The biocompatibility was evaluated through hemocompatibility tests and it was observed that the copolymers obtained were not cytotoxic. In base of the results, the chemical structure of these new copolymers confers a functionality that allows them to serve as nuclei to graft other molecules, such as polysaccharides. Then, the results obtained on the LCST temperature, porosity, interconnected pore network morphology, the ability to be injectable and the biocompatible nature of these copolymers are indicative that these new synthetic biomaterials have the potential to be used in biomedical, pharmacological and for tissue engineering. Also, once their biocompatibility was demonstrate, they may serve to generate interesting compounds having chemical anchor points for the possible addition of polysaccharides using insertion reactions, thereby generating graft copolymers with potential use in biomedical applications.

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36

Kuznetsova, Yulia L., Karina S. Sustaeva, Alexander V. Mitin, Evgeniy A. Zakharychev, Marfa N. Egorikhina, Victoria O. Chasova, Ekaterina A. Farafontova, Irina I. Kobyakova e Lyudmila L. Semenycheva. "Graft Polymerization of Acrylamide in an Aqueous Dispersion of Collagen in the Presence of Tributylborane". Polymers 14, n. 22 (13 novembre 2022): 4900. http://dx.doi.org/10.3390/polym14224900.

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Abstract (sommario):

Graft copolymers of collagen and polyacrylamide (PAA) were synthesized in a suspension of acetic acid dispersion of fish collagen and acrylamide (AA) in the presence of tributylborane (TBB). The characteristics of the copolymers were determined using infrared spectroscopy and gel permeation chromatography (GPC). Differences in synthesis temperature between 25 and 60 °C had no significant effect on either proportion of graft polyacrylamide generated or its molecular weight. However, photomicrographs taken with the aid of a scanning electron microscope showed a breakdown of the fibrillar structure of the collagen within the copolymer at synthesis temperatures greater than 25 °C. The mechanical properties of the films and the cytotoxicity of the obtained copolymer samples were studied. The sample of a hybrid copolymer of collagen and PAA obtained at 60 °C has stronger mechanical properties compared to other tested samples. Its low cytotoxicity, when the monomer is removed, makes materials based on it promising in scaffold technologies.

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Wang, Yiqing, James N. Wilson, Mark D. Smith e Uwe H. F. Bunz. "TEMPO-Substituted PPEs: Polystyrene-PPE Graft Copolymers and Double Graft Copolymers". Macromolecules 37, n. 26 (dicembre 2004): 9701–8. http://dx.doi.org/10.1021/ma048308o.

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38

Kutsevol, Natalia, Mykola Bezuglyi e Nataliya Melnyk. "Light Scattering and Viscosimetry Study of Star-Like Dextran-Graft-Polyacrylamide". Chemistry & Chemical Technology 3, n. 4 (15 dicembre 2009): 263–68. http://dx.doi.org/10.23939/chcht03.04.263.

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Abstract (sommario):

Dextran-graft-Polyacrylamide copolymers (D-g-PAA) with a polysaccharide backbone having different molecular weights (Mw = 20 000 and Mw = 70 000) and with various number of PAA-grafts per one Dextran macromolecule have been synthesized. Light scattering and viscometry investigations have shown that the internal structure of D-g-PAA copolymers depends upon the distance between PAA-grafts. Compactness of D20-g-PAA copolymers is lower in comparison with D70-g-PAA samples due to different conformations of PAA grafted chains: a “mushroom” conformation for D70-g-PAA and a “worm-like” one for D20-g-PAA samples.

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39

Bulychev, N., E. Kisterev, H. Reimann, C. Schaller e C. D. Eisenbach. "Ultrasonic Treatment Enhanced Surface Modification of Titanium Oxide by Tailor-Made Surface-Active Polymers". Eurasian Chemico-Technological Journal 11, n. 2 (6 aprile 2016): 121. http://dx.doi.org/10.18321/ectj305.

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Abstract (sommario):

The surface modification of titanium dioxide in aqueous dispersions of specially tailor-made periodic acrylic acid/isobutylene copolymers, poly(acrylic acid)/polystyrene graft copolymers, and hydrophobically modified polyethyleneoxide urethane (HEUR) by ultrasonic treatment was studied. The pigment surface modification by the above copolymers was comparatively investigated regarding conventional adsorption as contrasted to an ultrasonic treatment assisted procedure. The course and efficiency of the polymer adsorpption onto the pigment surface was quantified by electrokinetic sonic amplitude measurements. The higher efficiency of the pigment surface coating by the copolymers as achieved by ultrasonic treatment varies with the copolymer architecture and is a consequence of ultrasonically induced pigment surface activation.

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40

Safakas, Konstantinos, Sofia-Falia Saravanou, Zacharoula Iatridi e Constantinos Tsitsilianis. "Thermo-Responsive Injectable Hydrogels Formed by Self-Assembly of Alginate-Based Heterograft Copolymers". Gels 9, n. 3 (17 marzo 2023): 236. http://dx.doi.org/10.3390/gels9030236.

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Abstract (sommario):

Polysaccharide-based graft copolymers bearing thermo-responsive grafting chains, exhibiting LCST, have been designed to afford thermo-responsive injectable hydrogels. The good performance of the hydrogel requires control of the critical gelation temperature, Tgel. In the present article, we wish to show an alternative method to tune Tgel using an alginate-based thermo-responsive gelator bearing two kinds of grafting chains (heterograft copolymer topology) of P(NIPAM86-co-NtBAM14) random copolymers and pure PNIPAM, differing in their lower critical solution temperature (LCST) about 10 °C. Interestingly, the Tgel of the heterograft copolymer is controlled from the overall hydrophobic content, NtBAM, of both grafts, implying the formation of blended side chains in the crosslinked nanodomains of the formed network. Rheological investigation of the hydrogel showed excellent responsiveness to temperature and shear. Thus, a combination of shear-thinning and thermo-thickening effects provides the hydrogel with injectability and self-healing properties, making it a good candidate for biomedical applications.

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41

Lv, Sheng Hua, Yan Fen Ma, Rui Gong, Xiao Liang Yan e Ming Ming Hou. "Study on Preparation and Properties of Starch and 4-Phenolsuflonate Graft Copolymer with HRP Catalysis". Advanced Materials Research 129-131 (agosto 2010): 837–41. http://dx.doi.org/10.4028/www.scientific.net/amr.129-131.837.

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Abstract (sommario):

Degraded starch was reacted with 4-phenolsuflonate (PHS) in water in the presence of horseradish peroxidase (HRP) catalyst/H2O2/acetylacetone (ACAC) to give starch and PHS graft copolymers. The structure and properties of the graft copolymer are characterized by Fourier Transform Infrared spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR). The retanned leather exhibits excellent increased thickness and softness, good dyeing ability and eligible mechanical properties.

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42

Myrzakhanov, M. M., El-Sayed Negim, Mohammad Nasir e K. M. Azzam. "Synthesis and application of nonionic graft copolymers P(mPEG-g-MMA)". Kompleksnoe Ispolʹzovanie Mineralʹnogo syrʹâ/Complex Use of Mineral Resources/Mineraldik Shikisattardy Keshendi Paidalanu 1, n. 324 (6 settembre 2022): 64–70. http://dx.doi.org/10.31643/2023/6445.09.

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Abstract (sommario):

The goal of this research is to prepare novel amphiphilic graft copolymers (nonionic) based on hydrophilic poly (ethylene glycol) methyl ether (mPEG) and hydrophobic methyl methacrylate (MMA) at room temperature and pressure. To generate P(mPEG-g-MMA) grafts, poly (ethylene glycol) methyl ether (mPEG) was synthesized and grafted with varied ratios of methyl methacrylate (MMA) in the existence of benzoyl peroxide as an initiator utilizing a macro-free radical initiator procedure under the effect of heating in toluene. The research discussed in this paper looked at the possibility of using the synthesized graft copolymer P(mPEG-g-MMA) as a nonionic demulsifier in Petroleum Crude Oil Emulsions. The produced nonionic surfactants were assessed as water demulsifiers in oil emulsions that were noticeable at varying oil: water ratios at 60oC. According to the demulsifier chemical compositions as well as concentrations, the testing findings revealed that the dehydration rate of the prepared demulsifiers reached 100%. The optimal demulsifier dose was 300 ppm.

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43

Kumar, Deepak. "IMPROVE THE NATIVE CHARACTERISTICS OF POLYSACCHARIDES BY GRAFTING THROUGH THE GAMMA RADIATION: A REVIEW". Green Chemistry & Technology Letters 2, n. 3 (19 luglio 2016): 151–59. http://dx.doi.org/10.18510/gctl.2016.235.

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Abstract (sommario):

Polysaccharides are bio-degradable, inexpensive and easily available from consistent agricultural resources. Polysaccharides and their derivatives represent a group of polymer widely used in pharmaceutical and biomedical fields. The biodegradability of natural polymers reduces their shelf life. Grafting copolymerization technique is a most effective fascinating way for chemical modification of native characteristics of polysaccharides with maximum possibilities for improving the properties of polysaccharides and enhanced the range of exploitation.While the major difficulty facing us during synthesizing a graft copolymers reaction, is the lack of commercial methods of synthesis and lower percent graft yield. It is well known that the most important methods of synthesis engage the employ of chemical free radical initiator i.e. conventional based methods. Graft copolymerization through γ-radiation method is a better method of grafting in comparison to a chemical method and exhibits a great potential to synthesize the graft copolymers by virtue of its higher efficiency, low cost, higher thermal stability as well as enhanced the yield of the graft copolymer. Future prospective of irradiation technique would be significant impacts to develop of polymerization.

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Quynh, Tran Minh, Masaru Yoneyama, Yasuyuki Maki, Naotsugu Nagasawa e Toshiaki Dobashi. "Thermosensitive Micelles Composed of Poly(lactide)-g-Poly(NIPAM-co-HEMA) Graft Copolymers". Key Engineering Materials 459 (dicembre 2010): 51–56. http://dx.doi.org/10.4028/www.scientific.net/kem.459.51.

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Abstract (sommario):

Different poly(N-isopropylacrylamide-co-hydroxyethyl methacrylate) copolymers (P(NIPAM-co-HEMA)) were synthesized from N-isopropylacrylamide (NIPA) and hydroxyethyl methacrylate (HEMA) comonomers by both radical and radiation polymerizations for comparison. PLLA-g-P(NIPAM-co-HEMA) graft copolymers were synthesized from L-lactide and respective P(NIPAM-co-HEMA) copolymers by ring opening polymerization. Both NMR and FTIR analyses demonstrated the PLLA chains have been grafted on to the P(NIPAM-co-HEMA) backbone. These graft copolymers revealed the cloud point temperature higher than that of PNIPAM homopolymer as determined by optical transmittance. The graft copolymers self-assembled into micelles with regularly spherical structures as observed by atomic force microscopy (AFM). The properties of these graft copolymers are interesting for the drug delivery system.

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45

Nazzal, A. I., e G. B. Street. "Pyrrole–styrene graft copolymers". J. Chem. Soc., Chem. Commun., n. 6 (1985): 375–76. http://dx.doi.org/10.1039/c39850000375.

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46

Theryo, Grayce, Feng Jing, Louis M. Pitet e Marc A. Hillmyer. "Tough Polylactide Graft Copolymers". Macromolecules 43, n. 18 (28 settembre 2010): 7394–97. http://dx.doi.org/10.1021/ma101155p.

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47

Yu, Yitao, Jing Wang e Xu Wang. "Synthesis and properties of polysiloxane graft waterborne polyurethane modified with α-N,N-dihydroxyethylaminopropyl-ω-butylpolydimethylsiloxane". Journal of Polymer Engineering 33, n. 6 (1 settembre 2013): 527–33. http://dx.doi.org/10.1515/polyeng-2013-0050.

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Abstract In this study, α-N,N-dihydroxyethylaminopropyl-ω-butylpolydimethylsiloxane was used to prepare waterborne polyurethane-polysiloxane graft copolymer dispersions. α-N,N-dihydroxyethylaminopropyl-ω-butylpolydimethylsiloxane was synthesized via hydroxyl protection, alkylation, anionic ring-opening polymerization, hydrosilylation, and deprotection. Waterborne polyurethane-polysiloxane graft copolymers were prepared by the reaction of poly propylene glycol (PPG), toluene diisocyanate (TDI), 2,2-dimethylol propionic acid (DMPA), 1,4-butanediol (BDO), and α-N,N-dihydroxyethylaminopropyl-ω-butylpolydimethylsiloxane. The water absorption of copolymer films decreased from 163.9 to 17.3% when polysiloxane content increased from 0 to 5%. The tensile strength of the copolymer films increased from 14.0 MPa to 26.3 MPa and decreased when polysiloxane content was more than 3%. The results revealed that the properties of waterborne polyurethane-polysiloxane graft copolymer dispersions and films were improved by grafting polysiloxane chains to polyurethanes.

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48

Hazer, Baki. "Graft Copolymers by Free Radical Coupling Reactions. I. Polystyrene-Polybutadiene Graft Copolymers". Journal of Macromolecular Science, Part A 32, n. 1 (1 gennaio 1995): 81–90. http://dx.doi.org/10.1080/10601329508020317.

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49

Sun, Dachuan, e Yang Song. "Influences of the Periodicity in Molecular Architecture on the Phase Diagrams and Microphase Transitions of the Janus Double-Brush Copolymer with a Loose Graft". Polymers 14, n. 14 (13 luglio 2022): 2847. http://dx.doi.org/10.3390/polym14142847.

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The backbone of the Janus double-brush copolymer may break during long-term service, but whether this breakage affects the self-assembled phase state and microphase transitions of the material is still unknown. For the Janus double-brush copolymers with a periodicity in molecular architecture ranging from 1 to 10, the influences of the architectural periodicity on their phase diagrams and order–disorder transitions (ODT) were investigated by the self-consistent mean field theory (SCFT). In total, nine microphases with long-range order were found. By comparing the phase diagrams between copolymers of different periodicity, a decrease in periodicity or breakage along the copolymer backbone had nearly no influence on the phase diagrams unless the periodicity was too short to be smaller than 3. For copolymers with neutral backbones, a decrease in periodicity or breakage along the copolymer backbone reduced the critical segregation strengths of the whole copolymer at ODT. The equations for the critical segregation strengths at ODT, the architectural periodicity, and the volume fraction of the backbone were established for the Janus double-brush copolymers. The theoretical calculations were consistent with the previous theoretical, experimental, and simulation results.

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50

Koňák, Čestmír, Zdeněk Tuzar, Pavla Kopečková, Joseph D. Andrade e Jindřich Kopeček. "Association of Graft Copolymers of Alkyl Methacrylates with α-Methyl-ω-hydroxy-poly(oxyethylene) ethacrylates". Collection of Czechoslovak Chemical Communications 60, n. 11 (1995): 1971–85. http://dx.doi.org/10.1135/cccc19951971.

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Solution properties of the statistical copolymers of alkyl methacrylates (AMA) with α-methyl-ω-hydroxy-poly(oxyethylene) methacrylates (MPOEMA) (nonionic polysoaps) were studied using static and dynamic ligh scattering as a function of monomer composition and concentration in aqueous and methyl cellosolve solutions. The solubility of the copolymers in water was found to be dependent on molar contant of AMA. While copolymers with low content of hexyl methacrylate (HMA) (0 and 20 mole %) were directly soluble in water, forming true solutions with a low content of large swollen aggregates, copolymers with a higher content of HMA or lauryl methacrylate (LMA) were not directly dispersable in water. A special procedure, the stepwise dialysis from methyl cellosolve solutions against water, had to be used to prepare them in the pseudomicellar form. The copolymers were directly soluble in methyl cellosolve and its water solution containing up to 60 vol.% of water. Nevertheless, the light scattering experiments were dominated by light scattering of swollen particles of aggregated copolymer molecules. The copolymers were not soluble in the mixtures containing 70-100 vol.% of water. Paramaters of aggregates in the mixture with 60 vol.% of water and in pure water were found to be very similar.

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