Search results for "Copolymer"
showing 10 items of 1003 documents
Effect of Core-Crosslinking on Protein Corona Formation on Polymeric Micelles.
2021
Most nanomaterials acquire a protein corona upon contact with biological fluids. The magnitude of this effect is strongly dependent both on surface and structure of the nanoparticle. To define the contribution of the internal nanoparticle structure, protein corona formation of block copolymer micelles with poly(N-2-hydroxypropylmethacrylamide) (pHPMA) as hydrophilic shell, which are crosslinked-or not-in the hydrophobic core is comparatively analyzed. Both types of micelles are incubated with human blood plasma and separated by asymmetrical flow field-flow fractionation (AF4). Their size is determined by dynamic light scattering and proteins within the micellar fraction are characterized by…
Thermal stability of poly(styrene-b-methyl methacrylate) and poly(styrene-b-ethylene-co-1-butene-b-methyl methacrylate)
1993
The thermal stability of poly(styrene-b-methyl methacrylate) diblock copolymers (= P(S-b-MMA)) and poly(styrene-b-ethylene-co-1-butene-b-methyl methacrylate) triblock copolymers (=P(S-b-EB-b-MMA)) was investigated. Well-defined high molecular weight block copolymers with narrow molecular weight distribution (MWD) were molded at different temperatures in vacuum and the alteration of the MWD was sensitively monitored by gel permeation chromatography (GPC). Up to 240°C P(S-b-MMA) shows almost no broadening of the MWD. At higher temperatures low molecular weight polystyrene-rich portions are formed. The number average molecular weight (Mn) is strongly reduced. P(S-b-EB-b-MMA) triblock copolymer…
New hyaluronic acid based brush copolymers synthesized by atom transfer radical polymerization.
2013
Abstract In this work, an efficient method for the synthesis of hyaluronic acid based brush copolymers using atom transfer radical polymerization (ATRP) has been reported. At first, two different hyaluronic acid (HA) based macroinitiators have been prepared and then they have been used for the polymerization via ATRP of hydrophilic or hydrophobic molecules carrying vinyl portions. In particular, by linking 2-bromo-2-methylpropionic acid (BMP) to the primary hydroxyl groups of tetrabutyl ammonium salt of HA (HA–TBA) or to amino groups of the ethylenediamino derivative of HA–TBA (HA–TBA–EDA), two macroinitiators (HA–TBA–BMP and HA–TBA–EDA–BMP) have been obtained. Then they have been used for …
Polymerization of styrene
1979
Copolymerization of Isoprene with p-Alkylstyrene Monomers: Disparate Reactivity Ratios and the Shape of the Gradient
2019
The statistical copolymerization of isoprene with p-ethyl- (p-ES), p-isopropyl- (p-iPS), and p-tert-butylstyrene (p-tBS) initiated by sec-butyllithium in cyclohexane was investigated with respect to kinetics, reactivity ratios, and formation of tapered block copolymers with pronounced monomer gradient. An efficient synthetic route to the monomers was developed on a multigram scale, relying on the precipitation of the side-product triphenylphosphine oxide at low temperature. The copolymerization kinetics and resulting molecular weight distributions were analyzed. The dispersity, Đ, of the copolymers depends on the p-alkyl substituent, the the degree of polymerization Pn and the comonomer mol…
Hyperbranched Polyols via Copolymerization of 1,2-Butylene Oxide and Glycidol: Comparison of Batch Synthesis and Slow Monomer Addition
2015
Hyperbranched poly(butylene oxide) polyols have been synthesized by multibranching anionic ring-opening copolymerization of 1,2-butylene oxide and glycidol. Systematic variation of the composition from 24 to 74% glycidol content resulted in a series of moderately distributed copolymers (Đ = 1.41–1.65, SEC), albeit with limited molecular weights in the solvent-free batch process in the range of 900–1300 g mol–1 (apparent Mn determined by SEC with PEG standards). In situ monitoring of the copolymerization kinetics by 1H NMR showed a pronounced compositional drift with respect to the monomer feed, indicating a strongly tapered microstructure caused by the higher reactivity of glycidol. In the …
Blends of polyamide 6 and bisphenol-A polycarbonate. Effects of interchange reactions on morphology and mechanical properties
1992
Blends of polyamide 6 (PA6) and polycarbonate (PC) were prepared in a Brabender mixer, at 240°C, applying long mixing time, for 45 min. It was observed that the morphology and the mechanical properties tend to resemble those of a homogeneous material as the mixing time and PA6 concentration increase. This is attributed to chemical reactions taking place between the two homopolymers. Acidolysis, amidolysis, and aminolysis, catalyzed by the terminals and the amide groups of the polyamide, should in principle be possible. Our results indicate that the aminolysis is the main process, inducing simultaneously scission of PC chains and formation of PC-PA6 copolymer chains. The latter act as interf…
Racemic S ‐(ethylsulfonyl)‐ dl ‐cysteine N ‐Carboxyanhydrides Improve Chain Lengths and Monomer Conversion for β‐Sheet‐Controlled Ring‐Opening Polyme…
2020
The secondary structure formation of polypeptides not only governs folding and solution self-assembly but also affects the nucleophilic ring-opening polymerization of alpha-amino acid-N-carboxyanhydrides (NCAs). Whereby helical structures are known to enhance polymerization rates, beta-sheet-like assemblies reduce the propagation rate or may even terminate chain growth by precipitation or gelation. To overcome these unfavorable properties, racemic mixtures of NCAs can be applied. In this work, racemicS-(ethylsulfonyl)-dl-cysteine NCA is investigated for the synthesis of polypeptides, diblock and triblock copolypept(o)ides. In contrast to the polymerization of stereoregularS-(ethylsulfonyl)-…
Study of the molecular origin of the mechanical and dielectric β relaxation of methyl methacrylate/isopropenyl methyl ketone copolymers
1988
Resultats de l'etude dielectrique, mecanique et par TSC en faveur d'une combinaison d'une barriere intra- et intermoleculaire dans la relaxation beta