ABSTRACT

Abstract

The structures of ultra-thin films of vinylidene fluoride and trifluoroethylene copolymer were characterized using Fourier transform infrared reflection absorption spectroscopy (FTIR-RAS), FTIR transmission spectroscopy (FTIR-TRS), atomic force microscopy, and wide-angle X-ray diffraction. The ferro-electricity was determined from polarization charge (a displacement (D)–electric field (E) hysteresis). FTIR-RAS and FTIR-TRS measurements showed that the molecular chains of polymers (crystal c-axis) near the substrate tended to align parallel to the substrate. However, thermal annealing of the sample films at temperatures above 145 °C caused a marked change in molecular alignment of the polymer chains (crystal c-axis) from parallel to normal to the substrate, and, further, caused a conformation change from trans to partially gauche forms. Copyright © 2007 Society of Chemical Industry

Novel biodegradable network films with elastic properties were prepared from trimesic acid (Y) and poly(ethylene glycol)s (PEGs) with different molecular weights (MW) and/or 4,7,10-trioxa-1,13-tridecanediamine (I). Prepolymers prepared by a melt polycondensation were cast from N,N′-dimethylformamide solution and postpolymerized at 290°C for various times to form a network. The resultant films were transparent, flexible, and insoluble in organic solvents. The X-ray diffraction scattering pattern showed that all network films are amorphous. The densities of the network films decreased, whereas their water uptake increased with increasing MWs of PEG. The thermal and tensile properties were measured in dry and wet conditions and were affected remarkably not only by MWs of PEG, but also by the water uptake of the films. The glass transition temperatures (T_g) decreased with increasing MWs of PEG. YPEG₂₀₀ and YPEG₁₀₀₀ films showed good elastomeric properties with an ultimate elongation of 225 and 277%, respectively, in dry condition. The tensile strength of 13 MPa and Young's modulus of 214 MPa were the highest for YPEG₂₀₀ among the network elastic films studied. All sample films in wet condition had lower T_g's and tensile properties. The hydrolytic degradation was measured by the weight loss of network films in a buffer solution with or without Rhizopus delemar lipase at 37°C. The degree and the rate of the degradation increased with increasing MWs of PEG, which is compatible with the increase in water uptake of the films. Incorporation of large amount of I moiety into YPEG₁₀₀₀ film increased the glass transition temperatures, tensile strength and Young's modulus, but depressed elastic nature of the films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Summary: Biodegradable elastomeric network polyesters were prepared from multifunctional aliphatic carboxylic acids such as tricarballylic acid (Y_t) or meso-1,2,3,4-butanetetracarboxylic acid (X_b) and poly(ε-caprolactone) (PCL) diols with molecular weights of 530, 1 250 and 2 000 g · mol⁻¹. Prepolymers prepared by a melt polycondensation were cast from DMF solution and postpolymerized at 280 °C for various periods of times to form a network. The resultant films were transparent, flexible and insoluble in organic solvents. The network polyesters obtained were characterized by IR absorption spectra, WAXS, density measurement, DSC, and tensile test. Y_tPCL₁₂₅₀, and X_bPCL₁₂₅₀ network polyester films showed good elastomeric properties with high ultimate elongation (540–590%), and low Young's modulus (2.5–3.3 MPa). The enzymatic degradation was estimated by the weight loss of network films in a buffer solution with Rhizopus delemar lipase at 37 °C. The degree and rate of degradation were significantly affected by the molecular weight of PCL diol, chemical structures of multifunctional aliphatic carboxylic acids and the morphology of network films. The changes in the solid states of network films during the degradation were also estimated by the results of DSC and WAXS.