Search results for "Copolymer"
showing 10 items of 1003 documents
Critical Micelle Concentration of Micelles with Different Geometries in Diblock Copolymer/Homopolymer Blends
2011
Summary In this paper, we have investigated the shape transition ofanisolatedmicelleformedintheAB-diblockcopolymerandA-homopolymer blends. SCFT has been employed tocompute the CMC for three different morphologies:lamellar, cylindrical and spherical. By comparing theCMC for different shapes, we can determine the preferredmicelle geometry. Several factors can influence the micellemorphology,andwehaveexploredtheeffectsofthediblockasymmetry, the homopolymer/copolymer length ratio andthe monomer–monomer interaction, on the micelle shapetransitions. It is found the micelle undergoes a sequenceof shape transitions, lamellar ! cylindrical ! spherical,when the A-block of the copolymer becomes longer.…
Effect of CTBN rubber inclusions on the curing kinetic of DGEBA–DGEBF epoxy resin
2003
Abstract The curing kinetics of an epoxy resin matrix, based on diglycil ether of bisphenol A and F (DGEBA–DGEBF), associated with an anhydride hardener, at different carboxyl-terminated copolymer of butadiene and acrylonitrile liquid rubber (CTBN) concentration (0–10 phr) are studied using a differential scanning calorimetry (DSC) and a stress-controlled rheometer in isothermal and dynamic conditions. The aim of this work is to correlate the presence of the rubber phase with the transition phenomena that occur during the curing process. The CTBN rubber induces a catalytic effect on the polymerization of the pure resin clearly observed by a significant enhancement of the curing rate. Calori…
Hepatocyte-targeted fluorescent nanoparticles based on a polyaspartamide for potential theranostic applications
2015
Abstract Here, the synthesis of a galactosylated amphiphilic copolymer bearing rhodamine (RhB) moieties and its use for the preparation of polymeric fluorescent nanoparticles for potential applications in therapy and diagnosis are described. To do this, firstly, a fluorescent derivative of α,β-poly( N -2-hydroxyethyl)- d , l -aspartamide (PHEA) was synthesized by chemical reaction with RhB, and with polylactic acid (PLA), to obtain PHEA-RhB-PLA. Then, the derivatization of PHEA-RhB-PLA with GAL-PEG-NH 2 allows obtaining PHEA-RhB-PLA-PEG-GAL copolymer, with derivatization degrees in -PLA and -PEG-GAL equal to 1.9 mol% and 4.5 mol%, respectively. Starting from this copolymer, liver-targeted f…
Origin of nanostructural inhomogeneity in polymer-network gels
2017
Polymer-network gels often display nano- to microstructural spatial inhomogeneity of their polymer-segmental and crosslinking densities, especially if they are formed by uncontrolled free-radical crosslinking copolymerization of mono- and multifunctional monomers and crosslinkers. This structural complexity markedly affects their optical clarity, mechanical strength, and permeability, which is of central relevance for their performance in everyday-life and high-tech products. This review summarizes and inter-relates a rich amount of existing studies on the origin of this inhomogeneity. It arcs from early fundamental work in the 1990s, development and assessment of highly ideal and super tou…
Temperature Variation Enables the Design of Biobased Block Copolymers via One‐Step Anionic Copolymerization
2021
A one-pot approach for the preparation of diblock copolymers consisting of polystyrene and polymyrcene blocks is described via a temperature-induced block copolymer (BCP) formation strategy. A monomer mixture of styrene and myrcene is employed. The unreactive nature of myrcene in a polar solvent (tetrahydrofuran) at -78 °C enables the sole formation of active polystyrene macroinitiators, while an increase of the temperature (-38 °C to room temperature) leads to poly(styrene-block-myrcene) formation due to polymerization of myrcene. Well-defined BCPs featuring molar masses in the range of 44-117.2 kg mol-1 with dispersities, Ð, of 1.09-1.21, and polymyrcene volume fractions of 30-64% are acc…
Thioether-Bearing Hyperbranched Polyether Polyols with Methionine-Like Side-Chains: A Versatile Platform for Orthogonal Functionalization
2016
The synthesis of thioether-bearing hyperbranched polyether polyols based on an AB/AB2 type copolymerization (cyclic latent monomers) is introduced. The polymers are prepared by anionic ring-opening multibranching copolymerization of glycidol and 2-(methylthio)ethyl glycidyl ether (MTEGE), which is conveniently accessible in a single etherification step. Slow monomer addition provides control over molecular weights. Moderate dispersities (Đ = 1.48–1.85) are obtained, given the hyperbranched structure. In situ 1H NMR copolymerization kinetics reveal reactivity ratios of rG = 3.7 and rMTEGE = 0.27. Using slow monomer addition, copolymer composition can be systematically varied, allowing for th…
Aging of Nanosized ZnO Modified Polyoxymethylene Blends with Ethylene–octene Copolymer
2015
The influence of ethylene–octene copolymer and zinc oxide (ZnO) on structure and tensile stress–strain behavior of polyoxymethylene were investigated before and after ultraviolet weathering. Addition of ZnO considerably improved stress–strain characteristics of the ultraviolet-irradiation impaired composites. Crystallinities of ultraviolet-irradiated composites were affected by numerous competitive processes, including suppression of crystallization in the presence of multiple components in the system, nucleation induced by nanofiller, secondary crystallization and amorphization because of the chain scissions of the macromolecules. Addition of ZnO considerably improved stability of the comp…
Versatile, Multifunctional Block Copolymers for the Self-Assembly of Well-Defined, Nontoxic pDNA Polyplexes
2020
In the field of systemically applied, nucleic acid-based drugs, polyplexes are interesting candidates for therapeutic systems. In this study, we synthesized a multifunctional triblock copolymer via...
Synthesis and degradation of poly (2-hydroxyethyl methacrylate)-graft-poly (ε-caprolactone) copolymers
2004
Abstract Poly (e-caprolactone) macromonomers carrying a methacryloyl end groups were synthesized using different lanthanide derivatives as catalysts, and characterized by SEC and 1 H NMR. Hydrophilic–hydrophobic copolymers from macromonomers and 2-hydroxyethyl methacrylate (HEMA) were obtained by solution free radical polymerization. Depending on the feed ratio of the two components, different copolymer structures were obtained. The expected graft structure of the copolymers was confirmed by 1 H NMR. Thermal properties of the copolymers were determined by DSC and TGA. Hydrolytic and enzymatic degradations of the materials were performed. Poly (2-hydroxyethyl methacrylate)- graft -poly (e-ca…
The rate of polymerization in two loci reaction systems: VDF-HFP precipitation copolymerization in supercritical carbon dioxide
2011
When the copolymerization of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) is carried out in supercritical carbon dioxide (scCO 2) under heterogeneous conditions, the reaction occurs both in the continuous CO 2-rich phase and in the dispersed polymer-rich phase. The two phases being characterized by different values of reactant concentrations and kinetic parameters, one would expect that the reaction kinetics is affected by the polymer phase holdup in the reactor. However, the reaction rate is almost insensitive to the amount of produced polymer, at least at specific reaction conditions. This apparent contradiction is discussed and clarified in this paper by a series of comparativ…