Copolymer of dicyclopentadiene and cyclopentene (CPE) is synthesized through ring-opening metathesis polymerization using the second-generation Grubbs catalyst. The influences of monomer composition, catalyst concentration, and reaction temperature on gelification time and monomer conversion have been investigated. Furthermore, the reaction injection molding process is employed to produce the copolymer of dicyclopentadiene and CPE. It has been found that postcuring process is necessary to achieve 100% monomer conversion. The incorporation of a small amount of CPE into the copolymers can reduce the weight loss rate in the TGA process and improve the mechanical properties. The effects of CPE fraction, catalyst concentration, and postcuring temperature on thermal stability and mechanical properties are discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Melt mixing of polyamides results in exchange reaction and generation of copolymers. In this work, Monte Carlo method is used to simulate the time evolution of molecular weight distribution (MWD) and copolymer composition during the exchange reaction process between polyamides with AA and BC structure. The influences of initial composition and molecular weight have been investigated. Decrease in the difference between the average molecular weight of two kinds of polyamides results in faster approach of the MWD toward Flory's distribution and higher probability of producing copolymers. When the ratio between the numbers of initial molecules of two homopolymers is increased, the number of generated copolymers is reduced and the wider MWD is obtained. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

The aqueous precipitation copolymerization of acrylonitrile (AN) and vinyl acetate (VAc) with NaClO₃/NaHSO₃ redox initiation system is carried out continuously in a 10L pilot-plant reactor. The effects of pH value on ionization equilibrium of NaHSO₃, polymerization rate, particle morphology, particle size and its distribution, molecular weight and its distribution have been investigated. It has been found that effective concentration of reductant H₂SO₃ increases with the decrease in pH value. On the other hand, deceasing pH value intensifies the coalescence among particles and then reduces diffusion rate of monomer and radicals into particles. Experimental data shows that the increase of pH value results in higher conversion. It indicates that pH value's effect on particle stability prevails its influence on effective concentration of the reductant. This conclusion is verified by the molecular weight, particle size, and particle morphology. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Block copolymers, polystyrene-b-poly(styrene-co-maleic anhydride), have been prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization technique using three different approaches: 1-phenylethyl phenyldithioacetate (PEPDTA) directly as RAFT agent, mediated polystyrene (PS) block as the macromolecular PS-RAFT agent and mediated poly(styrene-maleic anhydride) (SMA) block with alternating sequence as the macromolecular SMA-RAFT agent. Copolymers synthesized in the one-step method using PEPDTA as RAFT agent possess one PS block and one SMA block with gradient structure. When the macromolecular RAFT agents are employed, copolymers with one PS block and one alternating SMA block can be produced. However, block copolymers with narrow molecular weight distribution (MWD) can only be obtained using the PS-RAFT agent. The MWD deviates considerably from the typical RAFT polymerization system when the SMA is used as the RAFT agent. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

High-density polyethylene grafted isotactic polypropylene (PP-g-HDPE) was prepared by the imidization reaction between maleic anhydride grafted polyethylene and amine-grafted polypropylene in a xylene solution. The branch density was adjusted by changes in the molar ratio between maleic anhydride and primary amine groups. Dynamic rheology tests were conducted to compare the rheological properties of linear polyolefins and long-chain-branched polyolefins. The effects of the density of long-chain branches on the rheological properties were also investigated. It was found that long-chain-branched hybrid polyolefins had a higher storage modulus at a low frequency, a higher zero shear viscosity, a reduced phase angle, enhanced shear sensitivities, and a longer relaxation time. As the branch density was increased, the characteristics of the long-chain-branched structure became profounder. The flow activation energy of PP-g-HDPE was lower than that of neat maleic anhydride grafted polypropylene (PP-g-MAH) because of the lower flow activation energy of maleic anhydride grafted high-density polyethylene (HDPE-g-MAH). However, the flow activation energy of PP-g-HDPE was higher than that of PP-g-MAH/HDPE-g-MAH blends because of the presence of long-chain branches. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The renaturation of lysozyme assisted by a novel type of hairy particles was investigated. The particles used consisted of polystyrene (PS) cores onto which long chains of thermosensitive poly(N-isopropylacrylamide) (PNIPAM) were grafted as shell. Here, two kinds of particles were synthesized as sub-micron PS cores and 89 nm brush thickness (Particle A) and 122 nm brush thickness (Particle B), respectively. Thermosensitive characteristics of the above prepared hairy uniform PS particles with PNIPAM brushes were studied and the results indicated that the lower critical solution temperature (LCST) of PNIPAM brushes grafted on the surface of uniform PS cores was between 33 and 34°C. It was proved that the particles were quite efficient in assisting lysozyme renaturation at high initial protein concentration. When the protein concentration was increased to 500 μg/mL, the refolding yield of the recovery of lysozyme activity could achieve 58.0% (Particle A) and 71.5% (Particle B), compared with only 34.8% by simple dilution refolding. Furthermore, the kinetics of lysozyme refolding in the absence and the presence of the colloidal particles were studied accordingly. The results indicated that the time required for the refolding with colloidal particles was a little bit delayed than that by the simple dilution method owing to the hydrophobic interactions between lysozyme and the PNIPAM brushes. The mechanism of the enhancement for the hairy uniform PS particles with PNIPAM brushes assisted refolding was further discussed. All results above demonstrated that the spherical PNIPAM brushes presented an alternative way to assist protein renaturation in vitro.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Ethylene–norbornene copolymers (ENC) with ∼ 50%, ∼ 25% and ∼ 15% norbornene (NB) fraction in a wide range of molecular weight were produced by metallocene catalysts. By coupling the gel permeation chromatography (GPC) with the intrinsic viscosity data in 1,2,4-trichlorobenzene (TCB)at 150°C, the Mark–Houwink parameters of ENC were determined and compared with previous classical analysis using polyethylene's relative parameters. The results indicated that parameter K was considerably increased with decreasing NB fraction in ENC but parameter α was only increased slightly. Furthermore, the structure characteristics and correlative rheological parameters of resultant ENC were also calculated and discussed by the Stockmayer–Fixman analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008