Melting transition temperature block copolymers

The physics of the glass transition in block copolymers are essentially the same as those of homopolymers, and little experimental attention has been devoted to this aspect. Ordered phases in block copolymer melts can be vitrified by cooling below the glass transition temperature of a glassy block, and indeed this is often the method for preparing samples for transmission electron... 

Microdomain stmcture is a consequence of microphase separation. It is associated with processability and performance of block copolymer as TPE, pressure sensitive adhesive, etc. The size of the domain decreases as temperature increases [184,185]. At processing temperature they are in a disordered state, melt viscosity becomes low with great advantage in processability. At service temperamre, they are in ordered state and the dispersed domain of plastic blocks acts as reinforcing filler for the matrix polymer [186]. This transition is a thermodynamic transition and is controlled by counterbalanced physical factors, e.g., energetics and entropy. 

The dynamic mechanical behavior indicates that the glass transition of the rubbery block is basically independent of the butadiene content. Moreover, the melting temperature of the semicrystalline HB block does not show any dependence on composition or architecture of the block copolymer. The above findings combined with the observation of the linear additivity of density and heat of fusion of the block copolymers as a function of composition support the fact that there is a good phase separation of the HI and HB amorphous phases in the solid state of these block copolymers. Future investigations will focus attention on characterizing the melt state of these systems to note if homogeneity exists above Tm. 

Thermoplastic elastomers (TPE), 9 565-566, 24 695-720 applications for, 24 709-717 based on block copolymers, 24 697t based on graft copolymers, ionomers, and structures with core-shell morphologies, 24 699 based on hard polymer/elastomer combinations, 24 699t based on silicone rubber blends, 24 700 commercial production of, 24 705-708 economic aspects of, 24 708-709 elastomer phase in, 24 703 glass-transition and crystal melting temperatures of, 24 702t hard phase in, 24 703-704 health and safety factors related to, 24 717-718... 

Fig. 2.5 Schematic showing the variation of inverse scattering intensity and domain spacing (as determined from SAXS or SANS) across the order-disorder transition of a block copolymer melt. The mean field transition temperature has been identified operationally as the point where, on heating, the inverse intensity crosses over to a linear dependence on T (after Sakamoto and Hashimoto 1995).

X = A + BIT, where A and B are constants). Thus S(q )should change linearly with 1/7. t his was indeed observed by Hashimoto etal. (1983b) at high temperatures however, at a temperature associated with the transition from the homogeneous disordered phase to the ordered phase, a deviation from linear behaviour was found. Such deviations are now ascribed to the effects of composition fluctuations (Bates et al. 1988 Lodge et al. 1996), and the crossover from linear to non-linear dependence of S(q ) on 1/7 does not correspond to the order disorder transition, rather the mean-field to non-mean-field transition (see Section 2.2.1 for block copolymer melts). 

Thermal Properties. The DPP portion of block copolymers crystallizes on heating at 290°C and then melts at 480°C. The DMP portion of block copolymers does not crystallize thermally but can be caused to crystallize by treatment with a suitable solvent, such as a mixture of toluene and methanol the crystallized DMP then melts at 258°C. The glass-transition temperatures of the homopolymers are too close (221°C for DMP, 228° for DPP) to permit observation of separate transitions, either in block copolymers or blends of the homopolymers. 

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