Effect Of Copolymer Structure Research Articles

Effects of Copolymer Structure on Enzyme-Catalyzed Polyester Recycling

Effects of Copolymer Structure on Enzyme-Catalyzed Polyester Recycling

Poly[(vinyl benzyl trimethylammonium chloride)]-based nanoparticulate copolymer structures encapsulating insulin

We report on the synthesis and preparation of four double hydrophilic polyelectrolytes and their complexation with insulin (INS). Specifically, two cationic-neutral poly[oligo(ethylene glycol) methacrylate]-b-poly[(vinyl benzyl trimethylammonium chloride)] (POEGMA-b-PVBTMAC) and two poly[oligo(ethylene glycol) methacrylate-co-vinyl benzyl trimethylammonium chloride] (P(OEGMA-co-VBTMAC)) copolymers are successfully synthesized by reversible-addition fragmentation chain transfer (RAFT) polymerization with different compositions. Based on light scattering techniques (DLS, ELS), the POEGMA81-b-PVBTMAC19, POEGMA46-b-PVBTMAC54 P(OEGMA90-co-VBTMAC10), P(OEGMA75-co-VBTMAC25) (subscripts denote wt.% composition of the components) copolymers are present as single chains and aggregates in aqueous media. A significant aggregation tendency of bare copolymers into well-defined spherical-shape particles is also noticed in cryogenic transmission electron microscopy measurements (Cryo-TEM) measurements. The synthesized copolymers were utilized as nanocarriers for insulin (INS) encapsulation. Nanocarriers were formed via electrostatic co-assembly, and the effects of copolymer structure on the properties of the formed hybrid copolymer-INS nanostructures are studied. Physicochemical results on the copolymer/INS complexes corroborated the efficient complexation of INS with copolymers. The determined characteristics and the morphology of the copolymer/INS complexes were found to depend on (−)INS/(+)polymer charge ratio. The copolymer/INS complexes retain the initial spherical shape of neat copolymer aggregates after the electrostatic complexation with INS, according to Cryo-TEM measurements, also uncovering the presence of aggregates and threadlike structures. FBS interactions between bare copolymers and copolymer/INS complexes manifested a good stability of the hybrid copolymer/INS assemblies into a simulated biological environment. Moreover, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy shows physical interactions between INS and the respective polyelectrolytes. Fluorescence spectroscopy (FS) measurements indicated no significant changes on the conformation of complexed INS.

DPD Simulations of Homopolymer–Copolymer–Homopolymer Mixtures: Effects of Copolymer Structure and Concentration

AbstractBlends prepared by mixing incompatible homopolymers with a compatibilizing copolymer attract high technological interest due to their self‐assembling behavior. In the present work, 281 dissipative particle dynamics (DPD) simulations are performed in order to evaluate the influence of copolymer microstructure and concentration on properties of these systems. The results show that alternate copolymers are arranged between the homopolymeric phases while nanodomains rich in each of the components are formed in the copolymeric matrix. Dispersion in block lengths increases the size of these nanodomains, so that they can properly allocate homopolymer chains. Besides, dispersions in chain lengths and chemical compositions of diblock copolymers, which can form self‐assembled mesostructures, also lead to development of larger mesophase domains. Larger dispersions of chain lengths and chemical compositions cause the increase of the amount of copolymers necessary to bring about changes in the mixing behavior, when compared to non‐dispersed copolymers. It can be concluded that microstructural properties of the copolymer exert a decisive impact on molecular interactions and, consequently, on the characteristics of the mesophases generated during the blending process. Therefore, microstructure control methods, stemming from both polymer‐reaction engineering and polymer‐purification techniques, are important for the design and resulting performance of the analyzed blends.

Thermal stability of ethylene copolymers with multi-alkenylsilsesquioxane comonomers synthesized by organometallic catalyst - Effect of copolymer structure

This study was focused on thermal properties of ethylene copolymers with di-, tri- and tetra-alkenylsilsesquioxanes (POSS) synthesized by ansa-metallocene complex. Ethylene copolymers with multi-alkenyl POSS were characterized by different thermal behavior depending on the kind of POSS comonomer and its content, as well as the copolymer structure. The copolymers differed in the incorporation way of POSS into the polymer chain (linear and crosslinked structure), content of specific unsaturation groups, molecular weight, as well as heterogeneity of polymer chain compositions. It was found that the kind and content of unsaturation groups in E/POSS copolymers played a significant role in the thermal stability of the obtained hybrid materials determined in non-isothermal conditions. Thus, linear copolymers showed higher thermal stability in comparison with neat polyethylene and crosslinked copolymers.Thermal stability of copolymers under iso-thermal conditions (1500 h heating at 100 °C) of polymeric products was primarily determined by the kind and content of silicon-oxygen POSS cage incorporated into the polymer chain. Incorporation of alkenylsilsesquioxane with completely condensed POSS cage into the polymer chain caused significant improvement of thermal stability, even in case of crosslinked copolymers, in contrast to comonomers with incompletely condensed silicon-oxygen POSS cage.

Effects of Copolymer Structure on the Mechanical Properties of Poly(dimethyl siloxane) Poly(oxamide) Segmented Copolymers

An investigation of the structure–property relationships of poly(dimethyl siloxane) (PDMS) polyoxamide segmented copolymers reveals the impact of oxamide spacing and PDMS molecular weight on physical properties. Varying the length of the methylene spacing between the oxamide hydrogen bonding groups in the hard segment (HS), as well as the PDMS soft segment molecular weight, provides insight into the influence on thermal and mechanical properties. Bulk polycondensation of ethyl‐oxalate‐terminated PMDS oligomers with diamines yields optically clear, thermoplastic elastomers with excellent mechanical properties. The structure–property investigation reveals optimum mechanical properties of PDMS polyoxamide segmented copolymers occur with the smallest spacing between oxamide groups in the HS. image

Cationic Graft Copolymer as a DNA B-Z Transition Inducer: Effect of Copolymer Structure

The biological importance of left-handed Z-DNA was supported by the identification of Z-DNA binding proteins. We previously reported that poly(l-lysine)-graft-dextran copolymers composed of a poly(l-lysine) main chain and dextran graft chains induced the B-Z transition under low salt conditions. Not only the cationic main chain but also the dextran grafts play an important role in induction of the B-Z transition. In this study, we prepared a series of poly(l-lysine) graft copolymers with different graft chains (dextran, poly(ethylene glycol) (PEG), or both) and graft contents to further elucidate the roles of copolymer structures and properties. The copolymers with higher graft contents more effectively stabilized the Z form of DNA than those having lower graft contents. An increase in the B-Z transition rate was observed as graft content increased. We propose that the side chains of the copolymers change microenvironmental factors, such as water activity and dielectric constant, around the DNA and stabilize the Z conformer. Interestingly, hetero graft copolymers with both dextran and PEG side chains stabilized Z-DNA more effectively than the homo graft copolymers with either dextran or PEG side chains.

Copolymers of amine methacrylate with poly(ethylene glycol) as vectors for gene therapy

A series of structurally related copolymers of tertiary amine methacrylate with poly(ethylene glycol) (PEG) were investigated for their potential to serve as vectors for gene therapy. The effects of copolymer structure on the complexation and transfection ability were assessed. The ability of the PEG-based copolymers and DMAEMA homopolymer to bind and condense DNA was confirmed by gel electrophoresis, ethidium bromide displacement and transmission electron microscopy. The presence of PEG in the copolymers had a beneficial effect on their ability to bind to DNA. Colloidally stable complexes were obtained for all the PEG–copolymer systems as shown by uniformly discrete spherical images from transmission electron microscopy and approximate diameters of 80–100 nm by dynamic light scattering studies. DMAEMA homopolymer, however, produced agglomerated particles, confirming the important role played by the PEG chains in producing compact stable DNA complexes. Assessment of the effect of ionic strength of the buffer on the complexation and dissociation of the complexes indicated the importance of both electrostatic and non-electrostatic interactions in the polymer–DNA complexation. In vitro transfection experiments showed that DMAEMA homopolymer gave the highest level of transfection comparable to a control poly- l-lysine (PLL) system. The PEG-based copolymers gave reduced levels of transfection, most likely due to the steric stabilization effect of a PEG corona.

Effect of copolymer structure on micellar behavior of acrylamide-octylphenylpoly (oxyethylene) acrylate surfactant

Acrylamide-octylphenylpoly (oxyethylene) acrylate copolymer (AM-C8PhEOnAc) surfactant is the copolymer of acrylamide (AM) and octylphenylpoly (oxyethylene) acrylate macromonomer (C8PhEOnAc). The effect of the copolymer structure on the micellar behavior in aqueous solution was studied using dynamic light scattering. It has been found that the length of ethylene oxide (EO) in the branch and the content of C8PhEOnAc in the copolymer surfactant have great effects on the size and distribution of the micelles. For AM-C8PhEO7Ac copolymer, at the concentration of 5 × 10−4 g/ml, the micellar size increases with the increase of C8PhEO7Ac content. However, for AM-C8PhEO10Ac copolymer, the result is the opposite; the micellar size decreases with the increase of C8PhEO10Ac content. Larger C8PhEOnAc content leads to narrower micellar distribution. For copolymer surfactants with equal C8PhEOnAc content, when the concentration of copolymer solution is the same, the copolymer with longer EO length forms smaller micelles.

Influência da estrutura de diferentes copolímeros de etileno e a-olefinas na funcionalização com anidrido maleico

A funcionalização de copolímeros de etileno e a-olefinas com anidrido maleico (AM) foi realizada em solução de xileno com peróxido de dibenzoíla (DBP) como iniciador. Foi estudado o efeito das diferentes estruturas dos copolímeros, como número e comprimento de ramificação, na incorporação do AM. A funcionalização também foi realizada em estado fundido utilizando-se um misturador Rheomix 600 e uma extrusora Rheocord 9000 da Haake. A funcionalidade foi determinada por titulometria de neutralização e os produtos foram caracterizados por espectroscopia na região do infravermelho (FT-IR) e por cromatografia de permeação em gel (GPC). A funcionalidade dos copolímeros de etileno com 1-hexeno aumentou com o aumento do teor de comonômero e dos copolímeros com 1-octeno e 1-deceno aumentou com o aumento do teor de a-olefina até um máximo, decrescendo e mantendo-se constante.

Photogenerated base in polymer curing and imaging: Design of reactive styrenic copolymers susceptible to a base-catalyzed ?-elimination

A novel family of functionalized styrenic copolymers that are susceptible to a base-catalyzed β-elimination reaction is reported. The reactive copolymers, poly-{(2-phenyl-2-cyanoethoxycarbonyloxystyrene)-co-(4-hydroxystyrene)}, are prepared by chemical modification of poly(4-hydroxystyrene) using 2-phenyl-2-cyanoethyl chloroformate. A photoresist material consisting of the copolymer and bis[[(2-nitrobenzyl)-oxy] carbonyl]-4,4′-trimethylenedipiperidine used as an amine photogenerator affords positive tone images by UV irradiation. The effect of copolymer structure and composition on imaging, thermal stability, and the ease of β-elimination reaction is discussed. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3543–3552 1997

Photogenerated base in polymer curing and imaging: Design of reactive styrenic copolymers susceptible to a base‐catalyzed β‐elimination

A novel family of functionalized styrenic copolymers that are susceptible to a base-catalyzed β-elimination reaction is reported. The reactive copolymers, poly-{(2-phenyl-2-cyanoethoxycarbonyloxystyrene)-co-(4-hydroxystyrene)}, are prepared by chemical modification of poly(4-hydroxystyrene) using 2-phenyl-2-cyanoethyl chloroformate. A photoresist material consisting of the copolymer and bis[[(2-nitrobenzyl)-oxy] carbonyl]-4,4′-trimethylenedipiperidine used as an amine photogenerator affords positive tone images by UV irradiation. The effect of copolymer structure and composition on imaging, thermal stability, and the ease of β-elimination reaction is discussed. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3543–3552 1997

Interpolymer association between random and graft acrylic copolymers with poly(ethylene imine): effects of copolymer structure

Interpolymer complex formation has been studied between acrylamide-vinyl alcohol graft copolymer, methacrylic acid-acrylamide random copolymer and polyethylene imine. Some blends of binary homopolymer complexes having the same proportion of interacting units as in copolymer complex have also been prepared. Stability constant, degree of linkage and related thermodynamic parameters (e.g. ΔG°, ΔH° and ΔS°) have been compared for the two complexation systems using Osada's methods. The comparative study indicated considerable difference in the values of these parameters, which has been explained on the basis of copolymer structure.

Interpolymer association between phenolic copolymers and polyelectrolytes: effects of copolymer structure and hydrophobic interactions on the stability of polycomplexes

Phenolic copolymers have been prepared with two different feed compositions from some typical phenolic monomers, such as, p-Chlorophenol, p-Cresol and p-Aminophenol. They have been characterized by known methods. Some interpolymer complexes of the phenolic copolymers have been prepared with polyelectrolytes, such as poly(methacrylic acid) (PMA) and poly(ethylene imine)(PEI). The degree of linkage, stability constant, enthalpy and entropy changes of the systems were determined at several temperatures. Interpretations have been sought in terms of the various interacting forces involved in the complex formation.

Electrical properties of poly(vinyl chloride) compositions

AbstractA sample of poly(vinyl chloride) (PVC) and a polar plasticizer consisting of dioctyl phthalate (DOP) and dibutyl phthalate (DBP) was prepared and found to possess inconvenient electrical properties (permittivity, dielectric loss, and conductivity). Different samples of PVC compositions were formulated from the PVC–DOP–DBP system and also variable proportions of a copolymer of 1‐octadecene‐maleic anhydride or its hexadecylester. Lead stearate as a heat stabilizer and kaolin as a filler were added. The effect of copolymer structure on the electrical properties of the PVC–DOP–DBP system was studied to obtain a plasticized PVC of good electrical insulation character. © 1993 John Wiley & Sons, Inc.