Block copolymers with incompatible components form various micro-phase separated structures. The type of micro-phase separation structure is determined according to the segregation power. Generally, the segregation power decreases with a temperature rise, which makes the morphology from the ordered state to the disordered state. Some research groups have investigated how the cross-linking influenced the thermal stability of micro-phase separated structures. These reports mostly used cross-linking such as thermal crosslinking and coordination bonding. In these past reports, the high heat or addition cross-linkers were required for the cross-linking, where the original morphology was inevitably affected by cross-linking. So, for more accurate investigation of correlation between cross-linking of domain in the microphase separated structures and the thermal-responsiveness, it is necessary to perform crosslinking without affecting original morphology. To realize this demand, we focus on photo cross-linking because crosslinking can be progressed at room temperature, and an ABA triblock copolymer with photo cross-linkable A blocks was prepared. The B chain component was poly(2-ethyl hexyl methacrylate) (PEHM), and the A chain component was poly(2-benzophenyloxyethyl methacrylate) (PBEMA) with benzophenone moieties which are photo cross-linkable groups. The P(BEMA-b-EHM-b-BEMA) (Mn = 3.2 × 104, Mw / Mn = 1.4, ΦA = 0.11) was prepared using two step ATRP. Subsequently, SAXS measurements were carried out to investigate the morphology. Scattering peaks of samples before and after photo cross-linking were almost same, which means photo cross-linking didn’t the original affect micro-phase separated structure. In SAXS measurement for the sample before photo cross-linking at elevated temperature, collapse of the micro-phase separation structure was observed at around 220 ° C. On the other hand, for the photo cross-linked sample, the micro-phase separation structure was retained even at 230 ° C. We succeeded in improving the thermal stability of micro-phase separated structure by cross-linking within the A chain domains.

Thermal stability enhancement of ABA triblock copolymers based on morphology by photo cross-linking the A blocks

256th National Meeting (2018)

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