Microphase separation in correlated random copolymers

In this paper we present the results of a calculation of the phase diagram of a highly polydisperse multiblock copolymer in the weak segregation limit. The theory for polydisperse systems developed by Erukhimovich and Dobrynin [Erukhimovich, I.; Dobrynin, A.V. Macromol.Symp, 81, 253 (1994)] has been used. The model of the copolymer has the following characteristics: the blocklengths, as well as the molecule lengths are highly polydisperse (M(w)/M(n) = 2). The average number of blocks per molecule is very large and the effects of the finiteness of the blocklengths (the fluctuation corrections) are ignored. The resulting phase diagram shows some remarkable differences with the phase diagram of a regular monodisperse multiblock. Known differences are e.g. the order of the transition from the homogeneous state, and the variation of the period of the microstructure with the chi-parameter. Ln addition, we found a peculiar feature at the critical point: the phase boundaries have discontinuous derivatives

Theory of microphase separation in multiple segment-type statistical multiblock copolymers with arbitrary block molecular weight distributions

A Landau free energy is derived for the weak segregation regime (WSR) of melts belonging to a very general class of statistical multiblock copolymers, referred to as “multiple segment-type statistical multiblock copolymers.” Copolymer chains in this class consist of sequences of up to M⩾2 chemically different types of segments, organized into sequences of blocks of varying lengths (molecular weights). The possible sequences of blocks that are encountered in the copolymer chains, as far as their type is concerned, are described by a first-order Markov process, while the block molecular weight distributions of these M types of blocks are completely arbitrary. The number of blocks per chain is assumed to be large. This class of copolymers is sufficiently general to encompass all industrial relevant bulk statistical multiblock copolymers, such as all known thermoplastic elastomers. The particular free energy considered is just one realization of an even more general Landau free energy which is applicable to the WSR of melts of all conceivable copolymers, including homopolymers and all possible blends. The derivation of this Landau free energy is given in Appendix A

Overview of active solar absorption/Rankine cooling program

The individual absorption and Rankine projects are identified, along with the main features and accomplishments/status of each and future plans. Included are four projects funded by SOLERAS, a joint US/Saudi Arabian effort. In the absorption program, there are three active component development projects, four systems field test projects, one advanced fluid study project and one advanced cycle study project currently funded by DOE. In the Rankine program, there are five active component development projects, two system field test projects, and one advanced study project. (LEW

The influence of disorder on the space charge field formation in photorefractive polymers

Recent holographic time-of-flight experiments in photorefractive polymers have shown the space charge field to depart from its expected behaviour. We show that this discrepancy arises due to the influence of disorder on the charge transport process.