Compatiblization of polymers via coalescence from their common cyclodextrin inclusion compounds

We have found, when inherently immiscible polymers are included as guests in the narrow channels of their common inclusion compounds (ICs) formed with host cyclodextrins (CDs) and then these polymer-1/polymer-2-CD-IC crystals are washed with hot water to remove the host CD lattice and coalesce the guest polymers, that intimately mixed blends of the polymers are obtained. This behavior had been observed previously by us for the crystallizable poly(epsilon -caprolactone) (PCL)/poly(L-lactic acid) (PLLA) pair, where in the coaelsced blend PCL and PLLA crystallinity was completely and nearly completely suppressed, respectively. Here we report similar observations made on the polycarbonate (PC)/poly(methyl methacrylate) (PMMA) pair, which are respectively difficult to crystallize and amorphous. PC/PMMA blends coalesced from their common gamma -CD-ICs are amorphous and generally exhibit single glass transitions at temperatures (T-g) between those of pure PC and PMMA. Interestingly, a 1:4 molar PG:PMMA blend coalesced from its common gamma -CD-IC is characterized by a T-g lower than that of pure PMMA. FTIR spectroscopy suggests an intimate mixing of and possible specific interactions between PC and PMMA chains in the coalesced blends as reflected by substantial shifts in the frequencies of the PMMA and PC C=O vibrations. In addition, repeated DSC scanning or annealing of the coalesced PC/PMMA blends for up to 2 h at T greater than or equal to 200 degreesC did not lead to phase separation as judged from the constancy of the single T-g's observed by DSC. Though not described in detail here, very similar results were also obtained for the PC/polystyrene (PS) pair, including a T-g for a PS-rich blend that is below the T-g for pure PS.We are currently studying the molecular-level mixing in and thermal stabilities of these blends.