FORMATION, CHARACTERIZATION, AND SEGMENTAL MOBILITIES OF BLOCK-COPOLYMERS IN THEIR UREA INCLUSION COMPOUND-CRYSTALS

We report the formation of crystalline inclusion compounds (ICs) betwe en the small-molecule host urea (U) and two block copolymer guests: (i ) poly(epsilon-caprolactone)-polybutadiene (PCL-PBD) and (ii) PCL-poly (ethylene oxide)-PCL (PCL-PEO-PCL). Both block copolymer-U-ICs are for med by cocrystallization from saturated solutions of urea, and each bl ock copolymer-U-IC was observed with DSC, X-ray diffraction, and C-13 NMR and FTIR spectroscopies. It was found that both blocks of the PCL- PBD diblock copolymer are included in the U-IC channels while only the terminal PCL blocks of the PCL-PEO-PCL triblock copolymer are include d. The structure of the PCL-PBD-U-IC appears to be a combination of th e traditional hexagonal form with narrow ca. 5.5 Angstrom channels sur rounding the PCL blocks, while the PBD blocks are included in an ''exp anded tetragonal'' structure observed previously for PEO(oligomer)-U-I C and polypropylene-U-IC, where the urea matrix channel diameter is be lieved to be expanded beyond 7 Angstrom. This might explain how the PB D blocks, which contain 12% 1,2 units with bulky -CH=CH2 side chains, are accommodated in the U-IC channels. Similarly, in the PCL-PEO-PCL-U -IC, where only the terminal PCL blocks are included, the IC structure appears very similar to the usual narrow channel, hexagonal structure as found, for example, in PCL-U-IC, the IC between the PCL homopolyme r and urea. As a consequence, we may observe PCL blocks in two distinc t U-IC environments and may compare their behaviors to those of PCL ch ains in the homopolymer PCL-U-IC and homopolymer and block copolymer b ulk crystals. In addition, T-1 rho measurements of H-1 spin diffusion reveal structural aspects of the block copolymer-U-ICs, and the isolat ion of U-IC included polymer chains from their neighbors may permit th e probing of 1-dimensional H-1 spin diffusion by observing the T-1 rho (H-1) relaxation in these block copolymer-U-ICs.