Microphase Separation of Polybutyrolactone-Based Block Copolymers with Sub-20 nm Domains

Reducing the crystallinity of PCL chains by copolymerization with substituted δ/ε-lactones and its impact on the phase separation of PCL-based block copolymers

Various substituted δ/ε-lactones have been copolymerized with ε-caprolactone (ε-CL) with the aim to inhibit the crystallization of polycaprolactone (PCL). Among the studied co-monomers, the best results were obtained with the...

Microphase separation/crosslinking competition-based ternary microstructure evolution of poly(ether-b-amide)

The temperature dependence of the rheological properties of poly(ether-b-amide) (PEBA) segmented copolymer under oscillatory shear flow has been investigated. The magnitude of the dynamic storage modulus is affected by the physical microphase separation and irreversible crosslinking network, with the latter spontaneously forming between the polyamide segments and becoming the dominant factor in determining the microstructural evolution at temperatures well above the melting point of PEBA. From the rheological results, the initial temperature of the rheological properties dominated by the microphase separation and crosslinking (T cross) structures were determined, respectively. Based on the two obtained temperatures, the microstructure evolution upon the heating can be separated into the ternary microstructure domains: homogenous (temperature below ), microphase separation dominating (between and T cross), and crosslinking dominating domains (above T cross). When the PEBA is heated to above T cross, the content of crosslinking network increases with time and temperature, leading to an irreversible and non-negligible influence on the rheological, crystallization, and mechanical properties. A more pronounced strain-hardening phenomenon during the uniaxial stretching is observed for the sample with a higher content of crosslinking network.

Polystyrene Chain Growth Initiated from Dialkylzinc for Synthesis of Polyolefin-Polystyrene Block Copolymers

Polyolefins (POs) are the most abundant polymers. However, synthesis of PO-based block copolymers has only rarely been achieved. We aimed to synthesize various PO-based block copolymers by coordinative chain transfer polymerization (CCTP) followed by anionic polymerization in one-pot via conversion of the CCTP product (polyolefinyl)2Zn to polyolefinyl-Li. The addition of 2 equiv t-BuLi to (1-octyl)2Zn (a model compound of (polyolefinyl)2Zn) and selective removal or decomposition of (tBu)2Zn by evacuation or heating at 130 °C afforded 1-octyl-Li. Attempts to convert (polyolefinyl)2Zn to polyolefinyl-Li were unsuccessful. However, polystyrene (PS) chains were efficiently grown from (polyolefinyl)2Zn; the addition of styrene monomers after treatment with t-BuLi and pentamethyldiethylenetriamine (PMDTA) in the presence of residual olefin monomers afforded PO-block-PSs. Organolithium species that might be generated in the pot of t-BuLi, PMDTA, and olefin monomers, i.e., [Me2NCH2CH2N(Me)CH2CH2N(Me)CH2Li, Me2NCH2CH2N(Me)Li·(PMDTA), pentylallyl-Li⋅(PMDTA)], as well as PhLi⋅(PMDTA), were screened as initiators to grow PS chains from (1-hexyl)2Zn, as well as from (polyolefinyl)2Zn. Pentylallyl-Li⋅(PMDTA) was the best initiator. The Mn values increased substantially after the styrene polymerization with some generation of homo-PSs (27-29%). The Mn values of the extracted homo-PS suggested that PS chains were grown mainly from polyolefinyl groups in [(polyolefinyl)2(pentylallyl)Zn]-[Li⋅(PMDTA)]+ formed by pentylallyl-Li⋅(PMDTA) acting onto (polyolefinyl)2Zn.