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Polymers and Materials Science	100%

Selected Abstracts

Mean-Square End-to-End Distance and Characteristic Ratio of Polyvinylene (Polyacetylene) Chains of Various Configurations

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2006
í Vohlídal
Abstract Summary: Closed-form analytical expressions are derived for the mean-square end-to-end distance of unperturbed polyvinylene chains of various configurational structure with freely rotating main-chain single bonds. In particular, expressions are derived for (i) stereoregular chains: all- trans, all- cis and cis - trans alternating; (ii) atactic cis - trans chains with a Bernoullian distribution of cis and trans units along the chain and various content of trans units, (iii) regularly segmented cis - trans chains [,cisy,transy,]n and (iv) diblock chains cisx,transy. The conformation factor is determined for several atactic polyvinylenes for which the unperturbed dimensions are available in the literature. [source]

Improving low-density polyethylene/poly(ethylene terephthalate) blends with graft copolymers

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008
D. E. El-Nashar
Abstract Blends of low-density polyethylene (LDPE) and poly(ethylene terephthalate) (PET) were prepared with different weight compositions with a plasticorder at 240°C at a rotor speed of 64 rpm for 10 min. The physicomechanical properties of the prepared blends were investigated with special reference to the effects of the blend ratio. Graft copolymers, that is, LDPE-grafted acrylic acid and LDPE-grafted acrylonitrile, were prepared with ,-irradiation. The copolymers were melt-mixed in various contents (i.e., 3, 5, 7, and 9 phr) with a LDPE/PET blend with a weight ratio of 75/25 and used as compatibilizers. The effect of the compatibilizer contents on the physicomechanical properties and equilibrium swelling of the binary blend was investigated. With an increase in the compatibilizer content up to 7 phr, the blend showed an improvement in the physicomechanical properties and reduced equilibrium swelling in comparison with the uncompatibilized one. The addition of a compatibilizer beyond 7 phr did not improve the blend properties any further. The efficiency of the compatibilizers (7 phr) was also evaluated by studies of the phase morphology (scanning electron microscopy) and thermal properties (differential scanning calorimetry and thermogravimetric analysis). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Development of Gelatin Hydrogel Pads as Antibacterial Wound Dressings

MACROMOLECULAR BIOSCIENCE, Issue 10 2009
Vichayarat Rattanaruengsrikul
Abstract Gelatin hydrogel pads have been prepared from a 10,wt.-% gelatin solution that contained 2.5,wt.-% AgNO3 in 70% v/v acetic acid by a solvent-casting technique. The AgNO3 -containing gelatin solution was aged under mechanical stirring for various time intervals to allow for the formation of silver nanoparticles (nAgs). The formation of nAgs was monitored by a UV-vis spectrophotometer. The morphology and size of the nAgs were characterized by transmission electron microscopy (TEM). To improve the water resistance of the hydrogels, various contents of glutaraldehyde (GTA) were added to the AgNO3 -containing gelatin solution to cross-link the obtained gelatin hydrogels. These hydrogels were tested for their water retention and weight loss behavior, release characteristics of the as-loaded silver, and antibacterial activity against Gram-negative Escherichiacoli and Gram-positive Staphylococcusaureus. The AgNO3 -containing gelatin solution that had been aged for 5 d showed the greatest number of nAgs formed. The size of these particles, based on TEM results, was 10,11,nm. With an increase in the GTA content used to cross-link the hydrogels, the water retention, the weight loss, and the cumulative amount of silver released were found to decrease. Finally, all of the nAg-loaded gelatin hydrogels could inhibit the growth of the tested pathogens, which confirmed their applicability as antibacterial wound dressings. [source]

Encapsulation and/or Release Behavior of Bovine Serum Albumin within and from Polylactide-Grafted Dextran Microspheres

MACROMOLECULAR BIOSCIENCE, Issue 4 2004
Tatsuro Ouchi
Abstract Summary: Polylactide (PLA)-grafted dextran (Dex- graft -PLA) of various contents of sugar units was synthesized by anionic polymerization of L -lactide (L -LA) using the alkoxide of partially trimethylsilylated dextran (TMSDex) and subsequently removing the trimethylsilyl (TMS) groups. The copolymer showed different solubility from L -LA homopolymer with increasing the content of sugar units. We prepared bovine serum albumin (BSA)-loaded microspheres (MS)s according to a water-in-oil-in-water emulsion-solvent evaporation/extraction method using methylene chloride/DMSO as an organic cosolvent. MSs prepared from Dex- graft -PLA [MS(Dex- graft -PLA)s] exhibited higher loading efficiency of BSA than MSs prepared from PLLA [MS(PLLA)s]. The in vitro release rate of BSA from MS(Dex- graft -PLA) was faster than that from MS(PLLA). BSA released from MS(Dex- graft -PLA) maintained the secondary structure of native BSA to a great extent, compared with BSA released from MS(PLLA). Confocal fluorescence images of the differential interference micrographs over the fluorescence images of MS(PLLA) and MS(Dex- graft -PLA). [source]

Direct Synthesis of PVA- g -PDMS in Microsuspension

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2008
Emmanuel Pouget
Abstract The synthesis of P(VA- co -VAc)- graft -PDMS copolymers has been achieved in microsuspension by direct reaction between an epoxy-terminated PDMS and some pendant alcohol groups in P(VA- co -VAc). In this synthesis, the copolymer is used both as dispersant and reactant. The hydrophilic/hydrophobic character of the final material can be varied at will by incorporating various contents of epoxy-functionalized PDMS through optimized reaction conditions. The final composition was determined by TGA and 1H NMR. Products prepared from monofunctional PDMS were easily redispersed in water whereas a film of crosslinked materials, arising from difunctional PDMS, showed the best waterproofing as shown by contact angle analysis. [source]

Specific interactions in ternary system quaternized polysulfone/mixed solvent

POLYMER ENGINEERING & SCIENCE, Issue 1 2009
Anca Filimon
Theoretical and experimental aspects on the specific interactions developed via electrostatic interactions and hydrogen-bonding in a ternary system formed of a proton-donor solvent (N,N -dimethylformamide or methanol), a proton-acceptor solvent (water), and a quaternized polysulfone with various contents of ionic chlorine, which indicates a proton-acceptor character, are investigated. Thus, the interactions of the ternary systems are corrected on the basis of the association phenomena defined through association constants. Numerical values for these constants were evaluated as a function of the system composition, by mathematical simulations for an accurate adjustment of preferential adsorption, determined by the Flory,Huggins,Pouchly theoretical approach applied to the experimental data. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers [source]