High-strength composite fibers were prepared from poly(vinyl alcohol) (PVA) and multiwalled carbon nanotubes (MWNTs) functionalized with PVA matrix. Esterification between MWNTs and PVA was confirmed by Fourier transform infrared, Raman spectroscopy, thermogravimetric analysis, transmission electron microscope, and atomic force microscope. Homogeneous dispersion of PVA-functionalized MWNTs in dimethyl sulfoxide was affirmed by optical micrographs and particle size analysis. The PVA-functionalized MWNTs/PVA (1 wt %) composite fibers prepared by gel spinning and hot-drawing process exhibited tensile strength and modulus as high as 2.1 and 34 GPa, respectively, showing a 75% increase in tensile strength and 35% increase in modulus compared with pure PVA fibers. The mechanical properties were also much higher than untreated MWNTs/PVA (1 wt %) composite fibers and carboxylated MWNTs/PVA (1 wt %) composite fibers. From wide-angle X-ray diffraction, scanning electron microscopy, and Raman spectra analysis, higher mechanical properties of PVA-functionalized MWNTs/PVA composite fibers are attributable to homogeneous dispersion of MWNTs in PVA matrix, stronger interfacial adhesion between MWNTs and PVA matrix, and uniaxial orientation of MWNTs along fiber axis. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Three kinds of modified poly(ethylene terephthalate) copolyesters were synthesized, using sodium-5-sulfo-bis-(hydroxyethyl)-isophthalate as the third monomer, 1,3-propanediol (PDO), 2-methyl-1,3-propanediol (MPD), and 2,2-dimethyl-1,3-propanediol (neopentyl glycol or NPG) as the fourth monomer, respectively. The copolyester fibers were also prepared by melt spinning and drawing processes. The effect of PDO, MPD, and NPG on the synthesis and spinning process was investigated, and the structures and properties of both copolyesters and the produced fibers were characterized. The results exhibited that the structural difference of PDO, MPD, and NPG played an important role in the synthesis and spinning process, and significantly affected the structures and properties of both copolyesters and the produced fibers, which thereby resulted in the difference in terms of dyeability improvement of copolyester fibers. The dyeing at boiling temperature under normal pressure experiments of copolyester fibers in both disperse dyebath and cationic dyebath revealed that incorporation of the fourth monomer could improve the dyeability of copolyester fiber, and copolyester fiber containing MPD unit had better dyeability due to a looser, more accessible structure when compared with the fiber containing PDO or NPG unit. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Poly(ethylene terephthalate) copolyesters (abbreviated as MCDP) containing 2-methyl-1,3-propanediol (MPD) and sodium-5-sulfo-bis-(hydroxyethyl)-isophthalate (SIP) units were synthesized through a direct polycondensation reaction. Chemical compositions of the copolyesters were determined by ¹H- and ¹³C- NMR spectroscopy, respectively. Thermal properties and isothermal crystallization behavior were characterized using DSC analysis. Results exhibited that the crystallization rate of MCDP copolyesters was depressed with increasing MPD content. The equilibrium melting temperature of MCDP copolyesters showed a marked decrease when the composition of MPD increased, indicating the incorporation of MPD units lead to less perfect crystals. The crystal structure was investigated via using WAXD patterns. It was confirmed that MPD and SIP can not enter into the crystal region. The crystal morphology observed by using POM clearly showed that the presence of MPD units depressed the crystallization ability of MCDP copolyesters. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

A novel cationic dyeable copolyester (MCDP) containing purified terephthalate acid (PTA), ethylene glycol (EG), 2-methyl-1,3-propanediol (MPD), and sodium-5-sulfo-isophthalate (SIP) was synthesized via direct esterification method. The chemical structure of modified cationic dyeable polyester (MCPD) was confirmed by FTIR and ¹H-NMR. The thermal properties of MCDP and cellulose acetate butyrate (CAB) blends with different blend ratios were investigated by DSC. The results revealed that MCDP and CAB were immiscible polymer blends, and the glass transition temperature of CAB in blend fibers was higher than that of CAB in blend chips because of the strengthening hydrogen bonding. The chemical changes of MCDP and CAB in blend melt spinning were analyzed. It was found that the thermal hydrolysis reaction of ester side groups of CAB occurred in blend melt spinning, which resulted in that the acid gas was produced and the hydroxyl group content of CAB was increased. Furthermore, the moisture absorption of blend fibers was improved about three times than pure MCDP fiber even after washing 30 times. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

BACKGROUND: The introduction of protein into polyacrylonitrile artificial muscle systems has been shown to be a good way to achieve quicker and better responses. This research work mainly focused on the structure and dynamic pH response of hybrid hydrolyzed polyacrylonitirile-blend-soy protein (H-PAN/SP) hydrogel fibers.

RESULTS: The micro-morphology and swelling/shrinking kinetics of H-PAN/SP hydrogel fibers were investigated using scanning electron microscopy and elongation/contraction experiments with different fiber diameters, concentration of crosslinker and temperature. The results revealed good consistency between Tanaka–Fillmore theory and the surface morphology of the multi-porous microstructures of the fibers. In addition, the crosslinking density and temperature had a great impact on the pH response of the hydrogel fibers, consistent with Flory–Huggins theory. Hydrogel fibers with a high content of soy protein showed an excellent and stable pH response.

CONCLUSION: Studies of dynamic elongation and contraction behavior assist in the understanding and control of the pH response of H-PAN/SP hydrogel fibers. Copyright © 2008 Society of Chemical Industry

BACKGROUND: Polyacrylonitrile (PAN) artificial muscles have attracted considerable attention for their fast responses. This research work is based on the preparation of novel pH-sensitive hydrogel fibers derived from hydrolyzed PAN and gelatin by wet spinning and chemical modification.

RESULTS: Through characterization of the fiber dynamic and static pH-sensitive behavior, pH response times were found to improve greatly with increasing gelatin content. At a weight ratio of 3 to 7 (PAN:gelatin), the best response times were obtained at 0.59 s for elongation and 1.14 s for contraction. Study of the chemical structures of hydrolyzed PAN and gelatin, as well as the surface morphology of the hydrogel fibers, indicated that the mechanism of formation of hydrogel fibers is closely interconnected with their pH-sensitive behavior. From the standpoint of the mechanism we also found that the addition of urea gave rise to hydrogel fibers with a controllable morphology, influenced by the pH-sensitive behavior.

CONCLUSION: The hydrogel system reported here is simple in preparation, but quite complex in chemical structure. The strong response of the fibers to pH provides some idea on the development of new artificial muscle systems. Copyright © 2008 Society of Chemical Industry

Novel smart hydrogel fibers were prepared from a blend of hydrolyzed-polyacrylonitrile (H-PAN) and soy protein (SP). The dynamic and static elongation/contraction behaviors were studied. It was discovered that H-PAN/SP hydrogel fibers consisted of a multiporous structure. With an increase in the content of SP, the hydrogel fibers exhibited excellent reversible pH-sensitive behavior. When the weight ratio of H-PAN to SP was 4 : 6, the hydrogel fibers showed the best response times at 1.35 s (elongation) and 0.63 s (contraction). Discontinuous volume phase transitions and hysteresis loops of the hydrogel fibers induced by changes in pH value were found. These results were found to be explicable in terms of the surface morphology and polyampholytic properties of H-PAN/SP hydrogel fibers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008