Scattering from disordered block copolymer

Mori K, Hasegawa H, Hashimoto T (1985) SmaU-angle scattering from bulk block copolymers in disordered state. Estimation of-values from accidental thermal fluctuations. Polym J 17 799-806... 

Experiments of Roe et al. [26] and Hashimoto et al. [27] demonstrated that scattering experiments on disordered block copolymers may also be used to determine x I parameters, using the RPA theory of Leibler [9]. In a subsequent paper, Fredrickson and Helfand showed that fluctuation corrections to the RPA are important in block copolymer melts [28]. When available, x parameters obtained from block copolymer melts are reported after fluctuation corrections have been incorporated, k values obtained from block copolymers are often [29,30] but not always [31] larger than those obtained in homopolymer blends. 

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).

Equation (16) derived from the random phase approximation is directly applicable to the mixture of block copolymers with homopolymers, provided that the correlation functions Sjj(q) in it are duly evaluated for the collection of ideal, independent chains in the mixture concerned. The equation gives the X-ray or neutron intensity s(q) scattered from such mixtures in the disordered state, and also leads to the prediction of the spinodal temperature. The MST itself is of more general interest, but because of the close relationship between MST and spinodal, the knowledge of the latter and its dependence on variables such as the size of the molecules and blocks involved is useful. 

SAXS and SANS have been used to determine the Fodt of microphase-separated block copolymers, by identifying the temperature at which the linearity of a plot of 1 /Im vs 1/r begins to show a discontinuity as the measurement temperature is increased from an ordered state or decreased from the disordered state [29,84,94,96, 99-101]. Also, Stiihn et al. [102] and Ehlich et al. [103] first introduced the concept of using the square of half width at the half maximum of the first-order scatter-... 

Stepanek P and Lodge T P (1996) Dynamic light scattering from block copolymer melts near the order-disorder transition, Macromolecules 29 1244-1251. 

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