Copolymer thermal glass transition temperature analysis

For all runs, thermal analysis of the resulting polymers showed that only one glass transition temperature could be found. This corresponded to the Tg of the VAc/VEOVA copolymer. Lower glass transition temperatures were found for the semibatch runs, perhaps due to slightly improved VEOVA incorporation. 

As expected for two-phase polymer systems, two glass transitions are detected for thermoplast grafted elastic siloxane particles by means of thermal analysis (DSC, DMTA) [10]. In Table 1, glass transition temperatures of elastic siloxane graft copolymer particles with different crosslink densities (1-20 mol% T units) and distinct thermoplastic shells (PMMA, PS) are listed. 

Thermal analysis are widely used for polymers and copolymers analysis. Glass transitions, melting, and decomposition processes are analyzed. Since the glass transition temperature Tg is marked by changes in the thermal capacity, expansion coefficient, and rigidity, TMA technique as well as DSC may be used. Tg increases with molecular mass up to certain values. Plasticizers and water depress this temperature. Thermal stability and influence of antioxidants and fillers may be analyzed by TG or DSC, under oxygen. 

Our intentions with these block copolymers were to develop a microphase separated matrix, and differential scanning thermal analysis of the P[MG8-4VP] diblock copolymers indeed showed the presence of two glass transition temperatures indicating microphase separation. The thermal transitions for the block copolymers are listed in Table 4. Depending on the block copolymer composition, a soft (oxyethylene) phase glass transition temperature (Tg) is observed between -60 and -45°C and a hard (4-vinylpyridine) phase between 135 and 143 C. The slight lowering of the of the hard phase relative to the 150°C of pure poly(4-vinylpyridine) is due to internal plasticization of the hard phase by the short... 

Roy and Biswas [140-142] synthesized the copolymer using I2 and FeCla to oxidize a mixture of both monomers in ethyl ether or toluene. Thermal analysis shows that the copolymer is more thermally stable than both homopolymers, and the glass transition temperature is intermediate between that of the homopolymers. XRD analysis indicates that the copolymer is less crystalline than polypyrrole. 

Two copolymers were synthesized with different ratios of the fluorene-based monomer and the fluorenylidene linker. Both polymers were obtained in high yields and high molecular weight with Mw = 55,000-89,500 Da and exhibited excellent thermal stability. Glass transition temperatures ranged from 153 °C to 197 °C with decomposition temperature (5% weight loss measurend by TGA analysis) of 440 to 450 °C. 

These are important fibers, used primarily as staple fibers in knitted textiles. The glass transition temperature of this polymer is stiU debated (it is somewhere between 85°C and 140 °C). Similarly, the heat of fusion of 100% crystalline polymer is not known exactly, and is somewhere between 317 °C and 335 °C (beyond the degradation temperature of the polymer). In addition, this polymer is strongly plasticized by water, and since most acrylic fibers are copolymers, their thermal analysis is complicated and not at all clear. For this reason no more time will be spent discussing these fibers. The interested reader is referred to a more detailed description by Jaffe et al. (1997). 

Nakano et al [160] prepared a copolymer of poly(vinyl acetate) and methacrylic acid by irradiation at 200 kHz. From measurements of viscoelasticity and from differential thermal analysis, it was concluded that the copolymer was of the block type. The glass transition temperature of this block copolymer was surprisingly reported to be much lower than those of random and graft copolymers. 

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