Thermal, Mechanical and Electrical Studies of Novel Shape Memory Polyurethane/Polyaniline Blends

Shape memory polymer （SMP） blends based on polyurethane （PU） and polyaniline （PANI） were prepared via chemical in situ polymerization process. The thermal, mechanical, electrical and shape memory properties were investigated. The structural characterization and morphology of the polymer blends were inspected by Fourier transform infrared （FTIR） and scanning electron microscopy （SEM）, respectively. The 1 wt% of PANI loading enhanced the thermal stability of the system up to 339 ~C. According to differential scanning calorimetry （DSC）, the glass transition temperature （Tg） and melting temperature （Tm） of PU/PANI blends increased with the polyaniline loading （0.1 wt%-l wt%）. Improved mechanical properties such as tensile strength and Young＇s modulus of PU matrix were also observed with PANI. Moreover, the electrical conductivity of PU/PANI blends was also found to be a function of PANI loading. Remarkable recoverability of thermally triggered shape memory （SM） behavior to the extent of 96% was achieved for 1 wt% PANI blend.

MECHANICALLY AND THERMALLY STABLE BLENDS OF POLY(STYRENE-BUTADIENE-STYRENE) WITH CONDUCTING POLY(THIOUREA-AZO-NAPHTHYL)

A new aromatic azo-polymer, poly（thiourea-azo-naphthyl） （PTAN）, has been synthesized using 1-（5- thiocarbamoylaminonaphthyl）thiourea and diazonium salt solution of 2,6-diaminopyridine. PTAN was easily processable using polar solvents and had high molar mass 57 × 10^3 g/mol. Electrically conducting, mechanically and thermally stable rubbery blends of poly（styrene-butadiene-styrene） （SBS） triblock copolymer and PTAN were produced by solution blending technique. FESEM of SBS/PTAN blends revealed nano-scale dispersion of the conducting filler showing good adhesion between the matrix and PTAN. Remarkable effects of azo-content on the conductivity of SBS-based blends have been observed. Accordingly, PTAN loading from 10 to 60 wt% increased the conductivity from 1.24 to 1.66 S/cm. Relationship between PTAN loading and thermal stability of the materials was also investigated. With increasing the PTAN content, 10% gravimetric loss was increased from 484 to 500 ℃, while glass transition was enhanced from 119 to 126 ℃. Thermal and conducting data of the blend showed better results relative to pure elastomer but were lower than those of the conducting filler. Similarly, the tensile strength （57.35-62.33 MPa） of SBS/PTAN was improved relative to there of SBS. Fine balance of properties renders new materials fairly better than the existing elastomeric blends used in a number of applications.

Synthesis and Properties of Melt Processed Poly(thiourea-azo-sulfone)/Carbon Nanotubes Nanocomposites

An aromatic azo-polymer, poly（thiourea-azo-sulfone） （PTAS）, has been prepared using 4-（4- aminophenylsulfonyl）benzenamine and diazonium salt solution of 2,6odiaminopyridine. PTAS was easily processable using polar solvents and had high molar mass 63 × 103 g.mo1-1 according to GPC. Mechanically and thermally stable and electrically conducting polymer/CNTs nano-composites were obtained via melt processing technique. Fine distribution of CNTs in a polymer matrix performed an essential role in the preparation of polymer/CNTs nano-composites based on interfacial interaction between CNTs and polymer matrix. Scanning electron micrographs showed good dispersion of filler and adhesion of matrix on the surface of nanotubes. Accordingly, increasing the amount of CNTs from 0.1 wt% to 5 wt% increased the electrical conductivity from 2.99 S.cm-1 to 3.56 S.cm-1. Mechanical strength of functional nanotubes-based hybrids was enhanced from 43.22 MPa to 65.02 MPa compared with that of hybrids with non-functional filler in matrix 37.21 MPa. A rapport between nanotube loading and thermal stability of the materials was also observed. 10% gravimetric loss temperature was increased from 528 ~C to 578 ~C, while glass transition was improved from 241 ℃ to 271 ℃. Adding up of small quantity of functional CNTs strongly affected the tensile, electrical and thermal properties of materials. Improvement of the physical properties of CNT-reinforced polymer nano-composites was ascribed to the melt processing technique.

Properties of Phosphoric Acid Doped Poly(benzimidazole/sulfone/siloxane/amide)/Sulfonated Polystyrene/Silica Nanoparticle-based Proton Exchange Membranes for Fuel Cells

New siloxane and sulfone containing poly（benzimidazole/sulfone/siloxane/amide） （PBSSA） has been prepared for the formation of hybrid membranes （PBSSA/PS-S/SiNPs） with sulfonated polystyrene （PS-S） and 0.1 wt%-2 wt% silica nanoparticles （SiNPs）. Field emission scanning electron micrographs showed good dispersion of filler, formation of dense nanoporous honeycomb like structure and uniform ionic pathway in these hybrids. The porous membrane structure was responsible for the fine water retention capability and higher proton conductivity of the new hybrids. Increasing the amount of nanoparticles from 0.1 wt% to 2 wt% increased the tensile stress of acid doped PBSSA/PS-S/SiNPs nanocomposites from 65.7 MPa to 68.5 MPa. A relationship between nanofiller loading and thermal stability of the membranes was also experientially studied, as the glass transition temperature of phosphoric acid doped PBSSAJPS-S/SiNPs nanocomposites increased from 207℃ to 215 ℃. The membranes also had higher ion exchange capacity （IEC） around 2.01 mmol/g to 3.01 mmol/g. The novel membranes with high IEC value achieved high proton conductivity of 1.10-2.34 S/cm in a wide range of humidity values at 80 ~C which was higher than that of perfluorinated Nafion 117 membrane （1.1 × 10^-1 S/cm） at 80 ~C （94% RH）. A H2/O2 fuel cell using the PBSSA/PS-S/SiNP 2 （IEC 3.01 retool/g） showed better performance than that of Nation 117 at 40 ℃ and 30% RH.