Copolymers dynamic mechanical analyses

Changes in heat capacity and measurement of T for blends have been used to determine components of copolymers and blends (126—129), although dynamic mechanical analysis has been found to give better resolution. Equations relating T of miscible blends and ratios of components have been developed from dsc techniques, eg, the Fox equation (eq. 1), where f the blend, or is the weight fraction of component 1 or 2,... 

Dynamic mechanical analysis of siloxane-urea copolymers show a sharp loss peak around —110 °C corresponding to the Tg of the siloxane segment. The transition in... 

Shown in Fig. 2 is the dynamic mechanical analysis of a representative copolymer series containing, in this case, varying aryl ether phenylquinoxaline compositions [44]. Two transitions were observed indicative of a microphase-sepa-rated morphology. For this copolymer series, the first transition was observed at... 

Various experimental techniques (dielectric relaxation, dynamic mechanical analysis, 1H, 2H and 13C solid-state NMR) have been used for investigating the secondary transitions of BPA-PC, and the block copolymers of BPA and TMBPA carbonates as well as compatible blends of BPA-PC and TMBPA-PC. They have provided lots of information on the motions of methyl, phenyl ring and carbonate units in bulk BPA-PC. The effect of intermolecular packing has also been clearly evidenced. 

The ft transition of a series of MGIMx copolymers has been investigated by dynamic mechanical analysis [80]. The temperature dependence of the loss modulus, E"y at 1 Hz is shown in Fig. 138. In the region of the a transition, when increasing the MGI content, a shift towards a higher temperature is observed. 

The approach developed in this paper, combining on the one side experimental techniques (dynamic mechanical analysis, dielectric relaxation, solid-state 1H, 2H and 13C NMR on nuclei at natural abundance or through specific labelling), and on the other side atomistic modelling, allows one to reach quite a detailed description of the motions involved in the solid-state transitions of amorphous polymers. Bisphenol A polycarbonate, poly(methyl methacrylate) and its maleimide and glutarimide copolymers give perfect illustrations of the level of detail that can be achieved. 

By tuning the relative composition and degree of polymerization (DP) of the two segments, phase-separated microstructures were formed in thin films of the copolymer. Specifically, dynamic mechanical analysis (DMA) and transmission electron microscopy (TEM) observations revealed that, for a small molar ratio of p(MA-POSS)/pBA (DP = 6/481/6), no evidence of microphase separation was evident while a large ratio (1 2 1) revealed strong microphase separation (Fig. 8) [122]. 

Kilburn, D., Bamford, D., Liipke, T., Dlubek, G., Menke, T. J., and Alam, M. A., Free volume and glass transition in ethylene/l-octene copolymers positron lifetime studies and dynamic mechanical analysis, Polymer, 43, 6973-6983 (2002). 

Several experimental approaches have been applied for determining the fiber Tg under hot wet conditions [199-203]. Aiken et al. [199] compared the Tg of a commercial acrylic yarn in the dry state and in water using dynamic-mechanical analysis, and observed a reduction from 92 to 72°C. Bell and Murayama [200] observed that the Tg of a commercial AN-NA copolymer decreased from 128°C when dry to 80°C in a 100% relative humidity atmosphere. Gur-Arieh and Ingamells [201] related the extension in length of Acrilan filaments to a Tg reduction and showed a shift from a 90°C in air to 57°C in water. Finally, Hori et al. [202] used DSC to show that the Tg of four kinds of acryhc fibers decreased with increasing water content and approached an almost constant value for all four fibers. 

The properties of the linear material 7.27 and the network copolymer 7.28 have been studied by dynamic mechanical analysis, DSC, and transmission electron microscopy. Evidence was obtained for the formation of highly ordered micro-phase-separated superstructures in the solid state from the materials 7.27. The Cu(bipy)2 moieties appear to form ordered stacks, and this leads to thermoplastic elastomer properties. In contrast, the network structure of 7.28 prevents significant microphase separation [51-53]. By means of related approaches, dinuclear Cu helical complexes have also been used to create block copolymers by functioning as cores [54], and polymer networks have also been formed by using diiron(II) triple helicates as cores for the formation of copolymers with methyl methacrylate [55]. 

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