Stereocomplexation of Polymers in Micelle Nanoreactors As Studied by Multiple Detection Thermal Field-Flow Fractionation.

In this study the thermally induced in situ stereocomplexation (SC) of binary blends of symmetrical isotactic and syndiotactic polymethymethacrylates (i- and s-PMMAs) inside micellar nanoreactors (MNR) with polystyrene (PS) shells is investigated using thermal field-flow fractionation (ThFFF) as a separation technique. The MNRs are prepared from three systematic binary blending ratios of pure micelles of i-PMMA-PS and s-PMMA-PS in a nonsolvent for PMMAs in order to produce mixed micelles with a binary microstructural composition of the interior PMMA cores. The SC of these stereoregular PMMA cores inside the MNRs is shown to be thermally induced as a function of annealing temperatures from room temperature up to 150 °C. This SC is initially confirmed by Fourier transform infrared spectroscopy (FTIR), whereby signal shifts are observed in the carbonyl absorption regions. These signal shifts are as a result of SC interactions between adjacent ester and alpha-methyl groups. Furthermore, temperature-dependent dynamic light scattering (DLS) results show that MNRs with more SC domains have a much more drastic reduction in size. Additional corroboration is provided by multiple detection ThFFF results which show significant differences in retentions and sizes between MNRs with stereocomplexed cores and those without. Ratios of i-PMMA:s-PMMA in the order of 1:1, 1:2, and 2:1 were investigated with all ratios exhibiting thermal annealing induced SC, of which the 1:2 ratio is shown to have the highest predisposition to SC.