In this paper the average helix orientation of surface-grafted poly(γ-benzyl L-glutamate) (PBLG), poly-(γ-methyl L-glutamate) (PMLG), and poly(γ-methyl L-glutamate)-co-(γ-n-stearyl L-glutamate) (PMLGSLG 70/30) was investigated by means of FT-IR transmission spectroscopy. The theoretical relation between the average tilt angle (θ) and the absorption peak areas of three different backbone amide bands could be calculated because their transition dipole moment directions with respect to the helix axis were known. From the normalized absorptions, the average tilt angles of grafted helices of PBLG, PMLG, and PMLGSLG 70/30 were determined. The somewhat larger average angle of PMLG helices of 35 ( 5°with respect to the substrate compared to the value of 32 ( 5°of PBLG was due to the higher grafting density of PMLG. Because of the smaller helix diameter as a result of the smaller size of the methyl side group, more PMLG helices grew on the same surface area. Sterical hindrance and unfavorable polar interactions between unidirectional aligned helices forced the PMLG helices in a more upright arrangement. The even more perpendicular orientation of PMLGSLG 70/30 (48 ( 6°) could be the result of incorporation of mainly γ-methyl L-glutamate N-carboxyanhydride (MLG-NCA) monomers during the initiation step. Incorporation of the much larger γ-n-stearyl L-glutamate N-carboxyanhydride (SLG-NCA) monomers afterward lead to enlarged angles with respect to the substrate. Due to swelling, a pronounced change in helix orientation of grafted PMLGSLG 70/30 in n-hexadecane was observed, resulting in an almost perpendicular helix orientation.

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 parameter. In addition, we found a peculiar feature at the critical point: the phase boundaries have discontinuous derivatives.

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.

Fluctuation effects on the order-disorder transition (ODT) in correlated random copolymers (polydisperse A/B multiblock copolymers with block lengths having an exponential Flory distribution, and a large average number of blocks per chain) are studied with due regard for the strong temperature dependence of the period of the arising ordered phases, characteristic for the system under consideration. To this end, following a field theoretical variational method, the free energy is minimized with respect to both the concentration profile ψ and the correlation function G, assumed to belong to certain classes of trial functions. The trial function for G contains an extra adjustable parameter as compared to the situation typical for monodisperse A/B block copolymer melts. The shape of the correlation function and its temperature dependence are determined both for the disordered phase and for the ordered phases. In the vicinity of the critical point the phase diagram is calculated and presented in a universal form by using reduced variables. It is shown that near the ODT and for A-monomer fractions f close to 1 /2, the profiles are strongly fluctuating: in the ordered phase the amplitude of the fluctuations is equal to the amplitude of the average profile, and in the disordered phase the concentration inhomogeneities are comparable to those in the ordered phase. In the same region the disordered phase has an anomalously large correlation length, indicating some kind of local ordering. In connection with this, we discuss the close relationship between the disordered phase and the random wave structure.

Influence of polydispersity on the phase behavior of statistical multiblock copolymers with Schultz-Zimm block molecular weight distributions Angerman, H.J.; Brinke, G. ten; Slot, J.J.M. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Abstract. In this paper we investigate in a systematic way the influence of polydispersity in the block lengths on the phase behavior of AB-multiblock copolymer melts. As model system we take a polydisperse multiblock copolymer for which both the A-blocks and the B-blocks satisfy a Schultz-Zimm distribution.In the limit of low polydispersity the expressions for the vertex functions are clarified by using simple physical arguments. For various values of the polydispersity the phase diagram is presented, which shows that the region of stability of the bcc phase increases considerably with increasing polydispersity. The strong dependence of the periodicity of the microstructure on the polydispersity and on the interaction strength is presented.