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Target Polymers (target + polymer)

Distribution by Scientific Domains

Polymers and Materials Science	100%

Selected Abstracts

Dispersion of graphite nanosheets in polymer resins via masterbatch technique

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007
Guohua Chen
Abstract The dispersion of graphite nanosheets (GNs) in polymer matrices via the masterbatch technique was investigated. Modifying resin was added to GNs to prepare blend which is designated as the masterbatch. Such masterbatches, containing 70,80 wt % of GN filler, were blended with target polymers via melt extrusion process to prepare polymer/GN nanocomposites. The extruded nanocomposites showed characteristic conducting percolation behaviors with the percolation thresholds mainly dependent on the miscibility of the modifying resin with polymer matrix. The percolation thresholds of AS (Acrylonitrile-Styrene compolymer)/GN and high-density polyethylene (HDPE)/GN nanocomposites prepared by this technique were about 9 and 14 wt % of GN, respectively. Scanning electron microscopy and other characterizations showed that the GNs were well dispersed in AS and HDPE resins. The extrusion process and compatibility of the modifying resin with target polymer proved to be important factors for the homogeneity of the nanodispersion. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3470,3475, 2007 [source]

Synthesis and characterizations of well-defined branched polymers with AB2 branches by combination of RAFT polymerization and ROP as well as ATRP

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2006
Bin Luan
Abstract A well-defined branched copolymer with PLLA- b -PS2 branches was prepared by combination of reversible addition-fragmentation transfer (RAFT) polymerization, ring-opening polymerization (ROP), and atom transfer radical polymerization (ATRP). The RAFT copolymerization of methyl acrylate (MA) and hydroxyethyl acrylate (HEA) yielded poly(MA- co -HEA), which was used as macro initiator in the successive ROP polymerization of LLA. After divergent reaction of poly(MA- co -HEA)- g -PLLAOH with divergent agent, the macro initiator, poly(MA- co -HEA)- g -PLLABr2 was formed in high conversion. The following ATRP of styrene (St) produced the target polymer, poly(MA- co -HEA)- g -(PLLA- b -PS2). The structures, molecular weight, and molecular weight distribution of the intermediates and the target polymers obtained from every step were confirmed by their 1H NMR and GPC measurements. DSC results show one T = 3 °C for the poly(MA- co -HEA), T = ,5 °C, T= 122 °C, and T = 157 °C for the branched copolymers (poly(MA- co -HEA)- g -PLLA), and T = 51 °C, T = 116 °C, and T = 162 °C for poly(MA- co -HEA)- g -(PLLA- b -PS2). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 549,560, 2006 [source]

Restraining the associations of anthracene fluorophore by chemically linking to poly(methyl methacrylate)

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008
Fu-Kun Su
Abstract Associations (dimer or aggregate) of anthracene (An) fluorophores tend to interrupt the monomer emission and reduce the quantum yield (,PL); therefore, poly(methyl methacrylate) (PMMA) chain was used in this study to chemically link to anthracene and to block the mutual associations among the anthracene fluorophores. With this aim, the target polymers were prepared by anionic polymerizations with 9,10-dibromoanthracene/s -butyllithium as initiating system to proceed polymerizations of methyl methacrylate (MMA) directly or in the presence of 1,1-diphenylethylene (DPE). Use of DPE before addition of MMA produces stable initiating anionic species and avoids potential side reactions during polymerization; however, it also introduces four ,-phenylene rings around the central anthracene ring, which interfere with the corresponding emission pattern and reduce the ,PL (32%) value due to potential interactions between phenylene rings and anthracene. On the contrast, polymerization without participation of DPE results in polymer with central anthracene ring directly connected to two PMMA chains, which gives clean vibronic emission pattern with limited association emissions and enhanced ,PL (52%) value. Physical blending of anthracene by PMMA is less efficient to restrain the associations and results in a film of lower ,PL (20%). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Dispersion of graphite nanosheets in polymer resins via masterbatch technique

An efficient synthetic route to well-defined theta-shaped copolymers

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2009
Gang-Yin Shi
Abstract A series of well-defined ,-shaped copolymers composed of polystyrene (PS) and poly(,-caprolactone) (PCL) with controlled molecular weight and narrow molecular weight distribution have been successfully synthesized without any purification procedure by the combination of atom transfer radical polymerization (ATRP), ring-opening polymerization (ROP), and the "click" chemistry. The synthetic process involves two steps: (1) synthesis of AB2 miktoarm star copolymers, which contain one PCL chain terminated with two acetylene groups and two PS chains with two azido groups at their one end, (,,,,-diacetylene-PCL) (,-azido-PS)2, by ROP, ATRP, and the terminal group transformation; (2) intramolecular cyclization of AB2 miktoarm star copolymers to produce well-defined pure ,-shaped copolymers using "click" chemistry under high dilution. The 1H NMR, FTIR, and gel permeation chromatography techniques were applied to characterize the chemical structures of the resultant intermediates and the target polymers. Their thermal behavior was investigated by DSC. The mobility decrease of PCL chain across PS ring in the theta-shaped copolymers restricts the crystallization ability of PCL segment. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2620,2630, 2009 [source]

Synthesis and characterizations of well-defined branched polymers with AB2 branches by combination of RAFT polymerization and ROP as well as ATRP

Synthesis of Well-Defined Figure-of-Eight-Shaped Polymers by a Combination of ATRP and Click Chemistry

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2008
Gang-Yin Shi
Abstract Well-defined figure-of-eight-shaped (8-shaped) polystyrene (PS) with controlled molecular weight and narrow polydispersities has been prepared by the combination of atom transfer radical polymerization (ATRP) and click chemistry. The synthesis involves two steps: 1) Preparation of a linear tetrafunctional PS with two azido groups, one at each end of the polymer chain, and two acetylene groups at the middle of the chain. 2) Intramolecular cyclization of the linear tetrafunctional PS at a very low concentration by a click reaction to produce the 8-shaped polystyrenes. The resulting intermediates and the target polymers were characterized by 1H NMR and FT-IR spectroscopy, and gel permeation chromatography. The glass transition temperatures (Tgs) were determined by differential scanning calorimetry and it was found that the decrease in chain mobility by cyclization resulted in higher Tgs for 8-shaped polystyrenes as compared to their corresponding precursors. [source]