Synthesis, Structure, and Properties of Alternating and Random Poly(styrene-b-butadiene) Multiblock Copolymers

Abstract

We report a synthetic method for the preparation of well-defined poly(styrene-b-butadiene) (PS-PB) n multiblock copolymers using a combination of living anionic polymerization and urethane based polycondensation along with an assessment of the associated microphase morphology and thermal and mechanical properties. The prepolymers, α,ω-dihydroxy polystyrene (HO-PS-OH) and α,ω-dihydroxy polybutadiene (HO-PB-OH), were prepared using a protected initiator, followed by deprotection and condensation with isophorone diisocyanate (IPDI) leading to the (PS-PB) n multiblock copolymers. Two types of block sequences were generated, one with random block sequences (PS-ran-PB) n and the second with alternating (PS-alt-PB) n block architectures. Size exclusion chromatography (SEC), 1 H nuclear magnetic resonance (NMR), and Fourier transform infrared spectrometry (FTIR) confirmed that the synthetic procedures yielded the desired products. Differential scanning calorimetry (DSC) revealed microphase separation and small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) demonstrated that the multiblock materials, containing between 69% and 85% by volume glassy PS, are characterized by a disordered bicontinuous-like morphology. Tensile tests demonstrated yielding followed by necking and an overall ductility that translates into much greater toughness than that typically found in glassy continuous SBS triblock copolymers.

Regulation of crystalline morphologies and mechanical properties of olefin multiblock copolymers by blending polymer with similar architecture of constituent blocks

“…This is usually achieved by changing the length or relative volume fraction of each component during the synthesizing. [13][14][15][16] However, it is comparatively difficult and uneconomical to change the process of synthesizing, especially for copolymers with sophisticated architecture such as multiblock copolymers. As for multiblock copolymers, changing the block number, block length or volume fraction may have enormous influence on the synthesizing method, and impurities as well as side reactions are not negligible with increasing block numbers.…”

“…However, up to now, little investigations have paid attention to the application of blending approach to multiblock copolymers, which may be attributed to the complex influence factors of morphology as well as properties for multiblock copolymers. Considering the complexity of synthesizing for multiblock copolymers, [13,14,17,24] it is quite essential to understand the interactions between multiblock matrix and blended polymers and regulate the apparent properties without changing the synthesizing process.…”

Monte Carlo Simulations of the Phase Separation of a Copolymer Blend in a Thin Film

“…This lamellar-in-lamellar structure is very similar to those found in multiblock copolymer self-assembly, [21][22][23][24][25][26][27][28][29] while the alternating and block copolymers in our copolymer blend system are much easier to be synthesized than that of asymmetric multiblock copolymers. [30][31][32] In this contribution, to explore the influence of system parameters such as segment distribution and segregation strength on phase separation, we design a series of polymer Monte Carlo simulations were carried out to study the phase separation of a copolymer blend comprising an alternating copolymer and/or block copolymer in a thin film, and a phase diagram was constructed with a series of composed recipes. The effects of composition and segregation strength on phase separation were discussed in detail.…”

Wide Bicontinuous Compositional Windows from Co-Networks Made with Telechelic Macromonomers

“…20,21 An alternative strategy to increasing polydispersity is greatly increasing the number of blocks to form multiblock chains. This approach enhances the likelihood of obtaining the bicontinuous phase 22,23 since multiblock chains face both kinetic and thermodynamic barriers to the formation of ordered structures. 22,24,25 Disordered bicontinuous phases from multiblock copolymers have demonstrated improved mechanical properties including higher stress and strain at break compared to analogous triblock copolymers.…”