Synthesis and Phase Separation Behaviour of High Performance Multiblock Copolymers

Abstract

The phase separation behaviour of block copolymers of the type (A-B) n (segmented block copolymers, multiblock copolymers) containing segments with different degrees of flexibility was investigated using a stepwise variation of the incorporated blocks A and B. Amorphous/rigid blocks (polysulfone segments) were systematically combined with amorphous/flexible blocks (poly(tetramethylene glycol), semiflexible/nematic blocks (different kinds of aromatic polyesters and poly(ester imides) as well as semicrystalline fluorinated polyester blocks). All multiblock copolymers were synthesized using a conventional transesterification polycondensation in the melt and the polycondensation results are discussed.The phase separation in the synthesized block copolymers was investigated both experimentally and theoretically. Flory-Huggins interaction parameters of the block copolymers were calculated and used together with mean field calculations in order to understand the phase separation behaviour of all block copolymers correlated to their chemical structure. On the other hand, the onset of phase separation in a series of block copolymers with a systematic variation of block molecular weights was examined experimentally, mainly by DSC and SAXS.Finally, the question is discussed whether or not the degree of phase separation in the investigated systems determines the properties of the polymers or not. This is for example outlined for the mechanical properties and, in particular, the surface properties of fluorinated block copolymers.

Modelling of the Phase Separation Behaviour of Semiflexible Diblock Copolymers

“…In Section 3 the resultant structure factor and spinodal diagrams consisting of the spinodal lines for various relevant parameters are presented. Finally, the discussion contains comparisons with previous calculations and with experimentally obtained data, [22] and some suggestions for future research.…”

“…We have choosen a real segmented block copolymer of (PSU-block-PTMO) n (PSU: Polysulfone, PTMO: Poly(tetramethylene oxide) which has blocks of very different chemical structure. [22] The molar masses of the diblock units of Table 2 and 3 can be recalculated to N and the mass fraction to molar fraction using the monomer parameters of Table 1, the block values of Table 4 and Equation (31) and (32).…”

“…Of course, the comparison given in Figure 6 has some insufficiencies like lacking polydispersity effects or the difficulties obtaining correct parameters. In the present study we have arbitrarily reduced the parameter from the value of 0:890 obtained by Pospiech et al [22] to 0:495 in order to place the phase-separated block copolymers into the heterogeneous region and the non-separated ones into the isotropic state. Note, that this artificial reduction of the parameter can be cut off, when different polydispersities are respected during spinodal calculations.…”

“…The theoretical approach is directed to reflect the experimentally observed unsymmetry of spinodals for copolymers built of blocks of different stiffness. [22] The form factor of a non-interacting semiflexible chain is obtained using a cumulant expansion to second order which gives a very compact and quite reliable expression for the structure factor of the interacting system. Additionally, our method does not need any anisotropic interaction i. e., Maier-Saupe parameters in opposite to the method used by Singh et al [11] The calculation model should respect the inner structure of the monomers by a weighted curvature of the segments.…”

Biodegradable polymeric micro‐nanofibers by electrospinning of polyester/polyether block copolymers

“…As known, polymers chemical composition and morphology influence the bulk properties (rheological behavior, mechanical properties). Block copolymers are of particular interest, because the combination of the single components can be balanced by using suitable molecular weights and amount of the coupled segments to obtain the characteristics required for the desired application 16–20. The mechanical properties are, in particular, an issue that has to be often faced when a material is implanted in the human body as temporary (e.g., bioerodible–bioeliminable scaffold) or permanent (e.g.…”