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Huai Yang – One of the best experts on this subject based on the ideXlab platform.
effects of functionality of thiol Monomer on electro optical properties of polymer dispersed liquid crystal filmsLiquid Crystals, 2017Co-Authors: Cuihong Zhang, Jiumei Xiao, Hangjun Ding, Fasheng Li, Haifeng Yu, Zhou Yang, Huai YangAbstract:
ABSTRACTIn this paper, polymer-dispersed liquid crystal (PDLC) films which based on the acrylate and the thiol Monomers were first prepared by ultraviolet-initiated polymerisation. The electro-optical properties and morphologies of the PDLC films were systematically investigated. The functionality of thiol Monomers and their feed ratio showed great influence on the properties of the fabricated PDLC films because of the existence of competition between thiol–acrylate reaction and acrylate Monomer polymerisation reaction. This made the polymer network and electro-optical properties of the PDLC films easily tunable by the introduction of the thiol Monomers. When added four-functional thiol Monomer PETMP with appropriate concentration into the PDLC system, lower driven voltage and higher contrast ratio were achieved.
effects of Monomer structure on the morphology of polymer networks and the electro optical properties of polymer dispersed liquid crystal filmsLiquid Crystals, 2012Co-Authors: Ping Song, Huai YangAbstract:
Polymer-dispersed liquid crystal (PDLC) films were prepared by photochemical polymerisation with a series of (meth)acrylate Monomers. The effects of Monomer structure on the morphology of polymer networks in the PDLC films were studied. The acrylate Monomers without sidegroup chain formed uniform polymer networks. The methacrylate Monomers with methyl as their sidegroup chains formed lace-like networks. The size of the LC droplets increased with increasing the length of the flexible chain of both methacrylate and acrylate Monomers. Meanwhile, the effects of the morphology of the polymer network on the electro-optical properties of PDLC films were also investigated.
Neil R Cameron – One of the best experts on this subject based on the ideXlab platform.
emulsion templated porous polymers prepared by thiol ene and thiol yne photopolymerisation using multifunctional acrylate and non acrylate MonomersPolymer, 2017Co-Authors: Chaoyi Chen, Neil R Cameron, Ahmed M Eissa, Tara L SchillerAbstract:
The chemical and mechanical properties of macroporous polymer substrates play a crucial role in the determination of their end-application. The preparation of highly (macro)porous monolithic polymers (polyHIPEs) by emulsion templating and thiol-ene/yne photopolymerisation, using multifunctional acrylate, allyl ether and alkyne-based Monomers with trimethylolpropane tris (3-mercaptopropionate) (TMPTMP), is described in this work. Issues associated with Monomer solubility and/or stability of the produced high internal phase emulsions (HIPEs) are tackled. Scanning electron microscopy (SEM) is used to study the morphology and porosity (average void diameters) of the obtained materials. Due to the nature of the photoinitiated thiol-ene reactions, materials obtained from acrylate Monomers display residual thiols that are quantified by a colourimetric (Ellman’s) assay. Raman specspectroscopy is also shown to be a complementary technique to evaluate the residual thiol content. The influence of the Monomer functionality on the mechanical properties of the material is explored using compression tests. Significant differences in the surface functionality and mechanical behavior between materials prepared with coMonomers able to homopolymerise (acrylates) and those unable to homopolymerise (allyl ethers; alkynes) are demonstrated.
Dennis C. Smith – One of the best experts on this subject based on the ideXlab platform.
development of glass ionomer cement systemsBiomaterials, 1998Co-Authors: Dennis C. SmithAbstract:
Abstract In the 1960s the idea of positive physico-chemical adhesion with tooth substance resulted in the invention of polyacrylic acid-based cements, first the zinc polycarboxylate and, subsequently, the glass-ionomer cements. These materials were shown to undergo specific adhesion with hydroxyapatite and proved to have properties satisfactory for a variety of clinical applications. The key properties of the glass-ionomer cements—fluoride release over a prolonged period and specific adhesion to enamel and dentine coupled with aesthetic qualities—are related to their characteristics as aqueous polyelectrolyte systems. In order to improve toughness, speed of setting and resistance to dehydration, hybrid materials in which some of the water content of the glass-ionomer system was replaced by water-soluble polymers or Monomer systems capable of ambient polymerization were formulated in the late 1980s. These materials, which have been termed resin-modified glass-ionomer cements, involve, ideally, the formation of an interpenetrating polypolymerwork combining the acid–base cross-linking reaction of the metal ion–polyacid with the cross-linking polymerization of the Monomer system or additive action of the polymers. In the predominantly resin materials there is little polyelectrolyte character and it is controversial whether such materials should be categorized as glass-ionomer cement systems. The specific advantages of these materials over traditional glass-ionomer systems and over composite restorative systems remain to be fully documented. Studies of adsoption to hydroxyapatite of typical Monomers using X-ray photoelectron specspectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF SIMS) indicate that resistance to water displacement decreases as hydrophobicity increases.
Chunyan Hong – One of the best experts on this subject based on the ideXlab platform.
hybrid copolymerization via mechanism interconversion between radical vinyl addition and anion ring opening polymerizationPolymer Chemistry, 2019Co-Authors: Ze Zhang, Tianyou Zeng, Decheng Wu, Wenjian Zhang, Chunyan HongAbstract:
Hybrid copolymerization of two or more structurally distinct Monomers (e.g., cyclic Monomers and vinyl-type Monomers) is very interesting because it can produce new types of copolymers and open up new research directions in the field of polymer chemistry. However, it has long been a challenge because the reactivity and polymerization mechanism of different Monomers are extremely different. Here, we report a new hybrid copolymerization via an interconvertible living free radical and anion ring-opening polymerization mechanism, in which the copolymerization of cyclic Monomers and vinyl-type Monomers can be achieved. Via this novel hybrid copolymerization, the cyclic Monomers and vinyl Monomers, which generally cannot be copolymerized, now can be copolymerized into one polymer chain. Furthermore, the Monomer arrangement in the chains could be easily regulated by the interconverting behavior. This new hybrid copolymerization will provide a powerful means for producing materials that have not been accessible by any other means.
Robert H Grubbs – One of the best experts on this subject based on the ideXlab platform.
examining the effects of Monomer and catalyst structure on the mechanism of ruthenium catalyzed ring opening metathesis polymerizationJournal of the American Chemical Society, 2019Co-Authors: William J Wolf, Robert H GrubbsAbstract:
The mechanism of Ru-catalyzed ring-opening metathesis polymerization (ROMP) is studied in detail using a pair of third generation ruthenium catalysts with varying sterics of the N-heterocyclic carbene (NHC) ligand. Experimental evidence for polymer chelation to the Ru center is presented in support of a Monomer-dependent mechanism for polymerization of norbornene Monomers using these fast-initiating catalysts. A series of kinetic experiments, including rate measurements for ROMP, rate measurements for initiation, Monomer-dependent kinetic isotope effects, and activation parameters were useful for distinguishing chelating and nonchelating Monomers and determining the effect of chelation on the polymerization mechanism. The formation of a chelated metallacycle is enforced by both the steric bulk of the NHC and by the geometry of the Monomer, leading to a ground-state stabilization that slows the rate of polymerization and also alters the reactivity of the propagating Ru center toward different Monomers in c…