Search

The poly[N,N-(dimethylamino) ethyl methacrylate] (PDMAEMA) macro-RAFT agent mediated dispersion polymerization of photo-responsive nitrobenzene-based monomer of o-nitrobenzyl methacrylate (NBMA) was performed and the polymerization kinetics and evolution of the block copolymer nanoparticles morphology during the RAFT dispersion copolymerization were investigated in detail. This dispersion RAFT polymerization underwent initial homogeneous polymerization at initial stage and then a subsequent stage of slowed heterogeneous polymerization occurred until the monomer conversion of the polymerization reaction is basically unchanged at about 50% at 24 h. The reason of deceleration of the second stage that is different from the second stage of acceleration for common monomer is discussed. The PDMAEMA-b-PNBMA nanoparticles were prepared by PDMAMEA-mediated RAFT dispersion polymerization, and the photo-response of PDMAEMA-b-PNBMA nanoparticles was also studied. [ABSTRACT FROM AUTHOR]

A self-switchable polymer reactor with a hyperbranched structure for controlled catalytic chemistry processes is reported. This polymer reactor was made of silver nanoparticles and a polymer carrier consisting of hyperbranched polyethylenimine and hydroxyethyl acrylate that behaved as thermally switchable domains. Below the transfer temperature, relatively strong catalytic reactivity was demonstrated due to the leading role of hydrophilic groups in the switchable domains, which opened access to the substrate for the packaged silver nanoparticles. In contrast, it showed weak catalysis at relatively high temperatures, reducing from the significantly increased hydrophobicity in the switchable domains. In this way, the polymer reactor displays controllable, tunable, catalytic activity based on this approach. This novel design opens up the opportunity to develop intelligent polymer reactors for controlled catalytic processes. [ABSTRACT FROM AUTHOR]

Molecular imprinting is a promising technique for the preparation of polymers with predetermined selectivity and high affinity. Normally, based on the self-assembly of functional monomers and templates (i.e., imprint molecules), the imprinted polymers are produced by crosslinking polymerizations. The templates are subsequently removed from the polymer, leaving behind binding sites complementary to the imprint species in terms of the shape and the position of functional groups. Recognition of the polymer constitutes an induced molecular memory, which makes the binding sites capable of selectively recognizing the imprint species. This article presents a limited review on molecular self-assembly and the uses of these imprinted polymers in separation, sensors, and catalysis. Other aspects including related backgrounds are also discussed. [ABSTRACT FROM AUTHOR]

Effect of β-cyclodextrin (CD) on methyl methacrylate dispersion polymerization forming poly (methyl methacrylate) (PMMA) particles was investigated. The presence of CD showed obviously effects on the polymerization, so as to increase the rate of polymerization and the conversion of monomer, as well as decrease the particle size. These effects were evidenced by the more increase in the CD content. The change of free energy derived from thermodynamic investigation in the present of CD was lower than that in the absence of CD. Also the monomer reactivity in the presence of CD is actually higher than that in the absence of CD. The decrease of free energy would be thermodynamically responsible for the increase of MMA conversion. The increase of monomer reactivity may take charge of increasing the polymerization rate. The dependency of particle size on CD content may be thermodynamically responsible for the change of macromolecular conformations of stabilizer due to the interaction of CD and stabilizer. [Copyright &y& Elsevier]

Abstract: Micron-grade monodisperse PMMA microspheres, whose surfaces were modified with functional groups by co-polymerisation using functional monomer, were prepared via dispersion polymerisation. Characterized by their large specific surface area, high adsorption ability, favourable biocompatibility, these monodisperse micron-sized PMMA microspheres were employed as the supporting material in the enzyme immobilization in present work. The influential factors on the activity of immobilized enzyme including pH, temperature, time etc were preliminarily investigated. The results concluded from the experiments indicated that the immobilization procedure could promote the resistance of enzyme against temperature, pH shift and some other tough reaction conditions meanwhile prolong the enzymatic lifetime for storage. [Copyright &y& Elsevier]

Highlights • A novel benzoxazine bearing amide and acetylene was synthesized. • Polymerization behaviors and curing kinetics were investigated. • The dielectric constant was reduced after benzoxazole formation. Abstract A novel ortho -amide functional benzoxazine monomer containing acetylene group has been synthesized in this study. The chemical structures of synthesized monomer are confirmed by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. The polymerization behaviors including both ring-opening polymerization of oxazine ring and polymerization of acetylene functionality are investigated by in situ FTIR and differential scanning calorimetry (DSC). The activation energy of polymerization has also been studied, and the activation energy of the polymerization is determined to be 104.4 kJ/mol and 103.1 kJ/mol, respectively, according to Kissinger and Straink methods. In addition, the benzoxazole formation during the thermal treatments is analyzed by solid state 13C NMR. The resulting thermoset derived from benzoxazine monomer exhibits excellent thermal stability and low dielectric constant, indicating its potential applications in aerospace, electronics industries and other composite areas requiring high performance polymeric matrix. [ABSTRACT FROM AUTHOR]

The preparation of hollow silica spheres via the sodium silicate route presents many advantages such as a low-cost silica source, and an environmentally friendly reaction system. Unfortunately, it is extremely hard to prepare the well-defined hollow silica spheres by using sodium silicate as the silica source owing to its rapid, disordered precipitation under the acid catalysis. As a result, we, in this paper, report a facile, economic, one-pot pathway for preparation of the ordered hollow silica spheres by employing a sodium silicate precursor. In this approach, the cationic polystyrene (CPS) templates can be first prepared via emulsifier-free emulsion polymerization by using the cationic monomer vinylbenzyltrimethylammonium chloride, then, the silica shells were attached on the surfaces of CPS particles via electrostatic interaction, finally CPS particles were in situ dissolved and removed by adding toluene to create ordered hollow silica spheres. Some modern techniques and instruments, including the transmission electron microscope, scanning electron microscopy, infrared spectroscopy, thermogravimetric analysis, and Brunauer-Emmett-Teller theory were employed to monitor and characterize the resulting hollow silica spheres. [ABSTRACT FROM AUTHOR]