A requirement for optimum performance in a pressure-sensitive adhesive (PSA) is the right balance between viscous and elastic properties, achieved by controlling the molecular architecture. Here, waterborne polyurethane PSAs are synthesized using a blend of polyether and polyalkene-based polyols. The effects of the polyol type and molecular weight on the adhesive and thermomechanical properties are explored to optimize them for PSA applications. A linear polyurethane is synthesized by the reaction of an aliphatic diisocyanate with a diol blend of polypropylene glycol (PPG) and hydroxyl-terminated polybutadiene (HTPB). With increasing concentrations of flexible HTPB segments and the associated increased viscous dissipation a favorable increase in the tack adhesion energy and peel strength is obtained. Adhesive properties are improved with increasing PPG molecular weight because chain entanglements become possible in the soft segments and raise the storage modulus. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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This work aims to experimentally clarify how the single chain conformation evolves as a function of grafting density for model comb-like chains in dilute solution in the whole density regime. Via a combination of rational design, precise synthesis and accurate characterization, we obtained four sets of PPA Nb-g-PS30-σ comb-like samples with well-defined architectures and accurately extracted their molecular parameters by triple detection size exclusion chromatography (TD-SEC). With these samples in hand, we quantified how the excluded volume interaction and chain conformation evolve with the grafting density (σ) in the whole density regime. Three main findings are reported: (i) the graft–graft excluded volume interaction is not ignorable even in the low σ-regime; (ii) contrary to theoretical predictions, both the excluded volume interaction and the chain conformation are found to be N b-dependent; (iii) both R g ∼ σ1/3 and [η] ∼ σ0 are experimentally confirmed for comb-like chains from different σ and N b, signifying a unique 3D mass-size growth pattern and a quasi-3D fractal feature. The obtained results help clarify some long-existed controversial issues in the field.

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Composite materials of poly (styrene-co-acrylonitrile) (luran) matrix with carbon fibers (CF)/carbon particles (CP)were prepared and their properties were evaluated. The mechanical and thermal properties of these composites were studied by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). Although, by increasing the filler concentration no significant difference was found in melting and crystallization temperatures of the luran. The storage and tensile modulus of the composites increased linearly with filler concentration up to 40 wt % that was approximately three times higher than that of the virgin luran. There is a shift in glass transition temperature of the composite with increasing the filler concentration and the damping peak became flatter that indicated the effectiveness of the filler-matrix interaction. The volume resistivity and thermal conductivity (TC) of the composites were also measured. At a given carbon filler content the CF-Luran composites have much less volume resistivity as compared to CP-Luran composites. The decreased percolation threshold and volume resistivity in case of CF-Luran composites indicated that conductive paths existed in the composites. The conductive pathways were probably formed through interconnection of the carbon fillers. The volume resistivity was also decreased as a function of temperature. The thermal conductivity was increased linearly as a function of temperature with increasing filler concentration up to 40% of CF and CP. This increase was more profound in case of CF-Luran as compared to CP-Luran composites. This was owing to greater thermal networks of fibers as compared to particles. POLYM. COMPOS., 28: 186 -197, 2007.

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A soluble polyamide was synthesized from aromatic and aliphatic monomers by condensing 4-aminophenyl sulfone with sebacoyl chloride in dimethylacetamide (DMAc) at low temperature under inert atmosphere. A stoichiometric amount of triethylamine was added to precipitate the HCl produced during the polymerization reaction. The precipitates were isolated, yielding a clear neat polyamide solution. Thin and transparent film achieved from the polymer resin was characterized for FTIR, NMR, gel permeation chromatography (GPC), thermogravimetry, differential scanning calorimetry, water absorption, and mechanical measurements. The dried film was found to be soluble in DMAc, DMSO, and DMF. The film-forming property of polyamide is being exploited for the preparation of the nanocomposites. Spectroscopic analyses confirmed the formation of polyamide. The values of M n , M w , and polydispersity as determined by GPC were found to be 9,779, 20,280 g/mol and 2.07 with RI detector whereas 10,133, 20,865 g/mol and 2.06 with UV detector, respectively. The thermally stable polyamide exhibited tensile strength (18.86 MPa), glass transition temperature (72.34 • C), and water absorption (16.1%). These studies further verified the related physical properties of the polyamide.