The synthesis of ultrathick concentrated poly-(methyl methacrylate) (PMMA) brushes by atom transfer radical polymerization (ATRP) was investigated. The reactions were performed with a catalyst system of Cu(I)Br/dinonyl-2,2′bipyridine (dN-bipy) and Cu(II)Br 2 /dN-bipy at 60 °C under a high pressure of 500 MPa. The equilibrium constant for this catalyst system was determined to be 1.5 × 10 −6 , which followed the kinetics study and indicated good polymerization rate control. Under the high pressure of 500 MPa, a micrometer scale thick PMMA brush was obtained. During chain growth under the high pressure, the concentration of the deactivator catalyst was demonstrated to significantly affect the graft density of PMMA brushes, which was correlated to the number of monomers added in activation−deactivation cycles. A novel "cutoff" experiment and gel permeation chromatography demonstrated similar propagation for free polymers and graft polymers even under high pressure.

Buckner (1988) extensively reviewed theoretical concepts proposed by a variety of scholars and developed the Neighborhood Cohesion Instrument (NCI) to measure three latent constructs (attraction to neighborhood, neighboring, and psychological sense of community). This instrument has been applied in most Western countries. The purpose of this research is to use Taiwan as a case study to assess whether the NCI can be applied to community research in an East Asian country. The authors apply confirmatory factor analysis to analyze two datasets collected in Taipei and the rural areas in Taiwan, separately. After scrutinizing the model fit indices and estimates of internal consistency, composite reliability and variance extracted, the authors conclude that the NCI can at least survey individuals in this particular East Asian country, Taiwan. By removing variables with small factor loadings and complex variables, researchers can develop a simplified model for further studies. © 2011 Wiley Periodicals, Inc.

Very-thick, concentrated brushes of poly­(methyl methacrylate) (PMMA) were synthesized by surface-initiated atom transfer radical polymerization in N,N-diethyl-N-methyl-N-(2-methoxyethyl)­ammonium bis­(trifluoromethanesulfonyl)­imide, an ionic liquid (IL) solvent. Notably, the high polymerization rate in this IL produced 700 nm-thick PMMA brushes, while the grafting density was observed to increase with increasing feed concentration of a deactivator catalyst (Cu­(II)­Cl2/ligand), suggesting that grafting density is significantly determined by chain growth during a single activation cycle. A concentrated PMMA brush, with a number-average molecular weight of 1.28 × 106, a polydispersity index of 1.23, a brush-layer thickness of 510 nm, and a grafting density of 0.30 chains nm–2, was successfully synthesized by taking advantage of the IL effect that provides a higher propagation rate constant and a lower termination rate constant. Further increases in the brush-layer thickness were achieved by moderately pressurizing the polymerization medium (i.e., by the combined use of the IL solvent and pressure), and an approximately 1 μm-thick concentrated polymer brush was conveniently synthesized at 50 MPa.

Comb-shaped poly(methyl methacrylate)s (PMMAs) with various mass fractions and various molecular weights of the side chains were prepared by free-radical polymerization followed by atom transfer radical polymerization (ATRP). The rheological properties were characterized in linear-viscoelasticity and in uniaxial extensional flow. Due to branching and thereby slow relaxation of the backbone, significant strain hardening was observed and well analyzed by the molecular stress function (MSF) model. The model parameter f max 2 increased with increasing M n,bb at almost constant M n,br and p, and with increasing p at almost constant Φ n,br , where M n,bb and M n,br are the number-average molecular weights of the backbone and the branched chains, and p and Φ n,br are the average number per backbone and the number-average mass fraction of the branched chains, respectively. These results provide guidelines for the polymer design with the aim of enhancing strain hardening in elongational flow.