Copolymers melting transition

K. Binder. Phase transitions in polymer blends and block copolymer melts some recent developments. Adv Polym Sci 772 181-299, 1994. 

Mortensen, K Brown, W Norden, B, Inverse Melting Transition and Evidence of Three-Dimensional Cubatic Structure in a Block-Copolymer Micellar System, Physical Review Letters 68, 2340, 1992. 

Binder, K. Phase Transitions in Polymer Blends and Block Copolymer Melts Some Recent Developments. VoL 112, pp. 115-134. 

The mean-field SCFT neglects the fluctuation effects [131], which are considerably strong in the block copolymer melt near the order-disorder transition [132] (ODT). The fluctuation of the order parameter field can be included in the phase-diagram calculation as the one-loop corrections to the free-energy [37,128,133], or studied within the SCFT by analyzing stability of the ordered phases to anisotropic fluctuations [129]. The real space SCFT can also applied for a confined geometry systems [134], their dynamic development allows to study the phase-ordering kinetics [135]. 

These concentration fluctuations are pivotal to the phase transitions in block copolymer melts and are dynamic in nature. They lead to a renormahzation of the relevant interaction parameters and are thought to be responsible for the induction of the first-order nature of the phase transition [264,265]. Such fluctuations are better studied in dynamic experiments. Thus, one can observe an increasing interest in diblock copolymer dynamics. These dynamic properties are being analysed through experimental, theoretical [266,267] and computer simulation approaches [268,269] with the aim of determining the main featirres of diblock copolymer dynamics in comparison to homopolymer dynamics. There are three main issues ... 

A novel approach is used to compatibilise a blend without addition of premade copolymers or functionalisation of polymers lacking functional groups. Solid-state shear pulverisation (S3P) processes polymers at temperatures below the melt transition (for semicrystalline polymers) or the glass transition (for amorphous polymers). The polymer, introduced as pellets or flakes into the pulveriser. 

The dynamics of block copolymers melts are as intriguing as their thermodynamics leading to complex linear viscoelastic behaviour and anisotropic diffusion processes. The non-linear viscoelastic behaviour is even richer, and the study of the effect of external fields (shear, electric. ..) on the alignment and orientation of ordered structures in block copolymer melts is still in its infancy. Furthermore, these fields can influence the thermodynamics of block copolymer melts, as recent work has shown that phase transition lines shift depending on the applied shear. The theoretical understanding of dynamic processes in block copolymer melts is much less advanced than that for thermodynamics, and promises to be a particularly active area of research in the coming years. 

The fascinating thermodynamics of block copolymers that results from microphase separation are the subject of the parts 2.2,2.3, and 2.4 of Chapter 2. Part 2.4 is concerned with the complex kinetic processes that accompany phase transitions, and the dynamic processes controlled by the structure of the block copolymer melt. 

The structure of block copolymer melts is usually trapped upon vitrification. The mechanisms underlying the glass transition are similar to those of the constituent homopolymers. Thus there is little distinct physics associated with the formation of solid phases by glassy block copolymers. 

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).

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