Structure and properties of tapered block polymers. 4. "Domain-boundary mixing" and "mixing-in-domain" effects on microdomain morphology and linear dynamic mechanical response

Abstract

A series of tapered block polymers of styrene-butadiene (S and P series) and styrene-isoprene (K series) were prepared by anionic polymerization, and the effects of composition variation along the main chain in the tapered block polymers on microdomain structure and on linear dynamic mechanical response were investigated. It was found that the effects are generally twofold: (i) enhancement of mixing of unlike segments in the interfacial region ("interphase") between two coexisting microphases ("domains") (i.e., enlargement of the interphase), designated as "domain-boundary" effect, and (ii) enhancement of mixing of unlike segments in the domains (or domain centers), designated as "mixing-in-domain" effect. The domain morphology and linear dynamic mechanical response were found to be predicted in terms of the two effects, the relative contribution being dependent upon the primary chemical structure. The morphological and mechanical behaviors of the ideal block polymer and S series can be predicted in terms of the domain-boundary effect, while those of the P and K series are dominantly affected by the mixing-in-domain effect.

Dynamic mechanical analysis of binary and ternary polymer blends based on nylon copolymer/EPDM rubber and EPM grafted maleic anhydride compatibilizer

“…This emphasizes that significant miscibility increase does not occur for the compatibilized blends. However, domain boundary mixing [40] or interface mixing [41] have been shown to cause an increased temperature dependence of storage modulus and increased level of loss modulus between T g for compatibilized relative to uncompatibilized blends. From the Figure 11 it is clear that 2.5% compatibilizer loaded blend shows the highest tanδ than other blends in various temperatures.…”

Morphology and mechanical properties of poly(methylmethacrylate)-b-poly(alkylacrylate)-b-poly(methylmethacrylate)

“…−20 to 90°C, which emphasizes a high degree of miscibility of the PMMA and the PnPA blocks. This increase in miscibility facilitates the relaxation of the individual copolymer chains [35][36][37], keeping tan δ high in a large temperature range. Fig.…”

Effect of sequence dispersity on morphology of tapered diblock copolymers from molecular dynamics simulations

“…A major driver of interest in such systems is that, by adjusting the length of the tapered region, one can tune microphase behavior and physical properties such as glass transition temperature (T g ) and orderdisorder transition temperature (T ODT ), as has been found in experiments by multiple groups. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] As would be intuitively expected, adding a taper generally increases the miscibility of the system, effectively decreasing the segregation strength (quantified by χN, the Flory χ parameter times polymer length) and widens the interfacial regions of the microphase separated structures. Furthermore, tapering has been shown to change the microphase behavior and dynamics versus typical diblocks in ways that cannot be explained by a simple shift in effective segregation strength.…”

“…26 One way tapered copolymers can be formed experimentally is via a semi-batch process of many sequential living anionic polymerization steps; during each step the two different types of monomers are injected in different amounts and are polymerized approximately randomly. 4,5,16,[27][28][29][30][31][32] A very recent work showed an excellent agreement between tapered copolymer density profiles from experiment and fDFT (with a fixed sequence), 17 though comparisons between experiment and theory with respect to order-disorder transitions or dynamics have not been as specific and precise.…”