Search results for "copolymer"
showing 10 items of 1003 documents
Acrylic thermoplastic elastomers and comb-shaped poly(methyl methacrylate) via the macromonomer technique
1996
Comb-shaped poly(methyl methacrylate) (PMMA) and poly(butyl acrylate) (PnBuA) grafted with PMMA were prepared by radical copolymerization of ω-methacryloyl-PMMA with MMA and nBuA, respectively. The comb-shaped PMMA is characterized with respect to radius of gyration by using gel permeation chromatography equipped with a multi-angle laser light scattering detector. The radical copolymerization of the macromonomer with nBuA in toluene follows complex kinetics. The dependence of the relative reactivity of the macromonomer on absolute concentration and on the ratio of comonomers may be explained by preferential solvation of comonomers by segments of their own kind (“bootstrap effect”) or even m…
Reductive Decationizable Block Copolymers for Stimuli-Responsive mRNA Delivery
2016
Messenger ribonucleic acids (mRNAs) are considered as promising alternatives for transient gene therapy, but to overcome their poor pharmacokinetic properties, smart carriers are required for cellular uptake and stimuli-responsive release. In this work, a synthetic concept toward reductive decationizable cationic block copolymers for mRNA complexation is introduced. By combination of RAFT block copolymerization with postpolymerization modification, cationic block copolymers are generated with disulfide-linked primary amines. They allow effective polyplex formation with negatively charged mRNA and subsequent release under reductive conditions of the cytoplasm. In first in vitro experiments w…
Blends of nylon 6 with a polyethylene functionalized by photooxidation
1990
An easy and cheap method to prepare functionalized polyethylene is reported in which polyethylene is photooxidized and then melt-blended with nylon. Structural, rheological, and mechanical modifications indicate that carbonyl, formed during photooxidation, and amine groups react giving rise to copolymers which stabilize the blends. Photooxidized polyethylene from waste could be very effective in preparing polyethylene/polyamide blends with improved properties. This new approach improves over current methods in which compatibilization of polyolefines and polyamides is mostly performed by reacting functionalized polyolefines with polyamides in molten state. The functionalization is achieved b…
Hyperbranched poly(glycolide) copolymers with glycerol branching points via ring-opening copolymerization
2015
Abstract Sn(Oct) 2 -catalyzed synthesis of hyperbranched poly(glycolide) copolymers with glycerol branching points in the backbone is possible via ring-opening multi-branching copolymerization (ROMBP) of glycolide and 5HDON (5-hydroxymethyl-1,4-dioxan-2-one). Using this strategy, well-defined and soluble branched polyesters with apparent molecular weights (M n ) in the range of 1300–2000 g mol −1 and varying comonomer content (5HDON/glycolide = 30:70–70:30) were obtained. 2D NMR spectroscopy, thermal analysis and MALDI-TOF mass spectrometry confirmed the successful incorporation of both monomers and the resulting branched structure. Multiple end group functionality offers the possibility fo…
Blends of poly(2,6-dimethyl-1,4-phenylene oxide) with styrene copolymers
1994
Binary blends of poly(2,6–dimethyl–1,4–phenylene oxide) (PPE) with various styrene copolymers were investigated. Poly(styrene–co–acrylonitrile) (SAN), poly[styrene–co–(methyl methacrylate)] (SMMA), poly[styrene–co–(acrylic acid)] (SAA) and poly[styrene–co–(maleic anhydride)] (SMA) are only miscible with PPE when the amount of comonomer is rather small. From calculated binary interaction densities it can be concluded that the strong repulsion between PPE and comonomer limits miscibility. In blends of PPE with SAN, as well as with ABS, the inter-facial tension between the blend components is significantly reduced upon addition of polystyrene–block–poly–(methyl methacrylate) diblock copolymers…
Tapered Multiblock Copolymers Based on Isoprene and 4-Methylstyrene: Influence of the Tapered Interface on the Self-Assembly and Thermomechanical Pro…
2019
The synthesis of tapered multiblock copolymers by statistical living anionic copolymerization of a mixture of isoprene (I) and 4-methylstyrene (4MS) in cyclohexane is based on vastly different reac...
Isoprene/Styrene Tapered Multiblock Copolymers with up to Ten Blocks: Synthesis, Phase Behavior, Order, and Mechanical Properties
2018
The living anionic copolymerization of isoprene and styrene in cyclohexane affords tapered block copolymers due to the highly disparate reactivity ratios of rI = 12.8 and rS = 0.051. Repeated addit...
The effect of THF and the chelating modifier DTHFP on the copolymerisation of β-myrcene and styrene: kinetics, microstructures, morphologies, and mec…
2022
The statistical anionic copolymerisation of the biobased monomer β-myrcene with styrene in cyclohexane was investigated via in situ near-infrared (NIR) spectroscopy, focusing on the influence of the modifiers (i.e., Lewis bases) tetrahydrofuran (THF) and 2,2-di(2-tetrahydrofuryl)propane (DTHFP) on the reactivity ratios. With increasing [modifier]/[Li] ratio, the reactivity ratios in the system myrcene/styrene are adjustable from rS ≪ rMyrvia rS ≈ rMyr to rS ≫ rMyr. The bidentate modifier DTHFP affects the reactivity ratios much more than THF: minute amounts only (0.35 equivalent relative to Li) are required to randomize the copolymer, and one equivalent to invert the reactivity ratios. Usin…
Diene/polar monomer copolymers, compatibilisers for polar/non-polar polymer blends. A controlled block copolymerisation with a single-site component …
2002
A well-controlled two-step process, the polymerisation of isoprene or isoprene/hex-1-ene copolymerisation followed by e-caprolactone polymerisation, affords trans-polyisoprene or (trans-polyisoprene/hex-1-ene copolymer)–poly(e-caprolactone) diblocks of various lengths. The single component initiator is an allylsamarocene compound. An atomic force microscopy study shows that these copolymers are efficient compatibilisers for poly(e-caprolactone) and polyisoprene blends. Poly(e-caprolactone) chain growth from Sm–polyisoprene chain.
Gradient high-performance liquid chromatography of statistical and block copolymers of styrene and t-butyl methacrylate
1989
Copolymers of styrene (S) and tert-butyl methacrylate (TBMA) containing 24–92 mass % of the latter monomer were investigated using a silica column with isooctane/tetrahydrofuran (THF) gradients and on a phenyl bonded-phase column by methanol (MeOH)/THF gradients using UV detection. In both cases, retention decreased with increasing TBMA content of the sample. This is in contrast to the behavior of copolymers of S and methyl methacrylate (MMA) whose retention in gradient elution on silica columns increases with MMA content due to the polarity of this unit. The inversion of elution order is a result of the bulky TBMA residues shielding the polar groups of the ester units. For copolymers of va…