Functional Macromolecules Of Novel Chiral Block Design, Synthesis And Self-assembly

The work in this dissertation mainly focused on stereocomplexe formation in block copolyester and it would be composed of two parts. The first part presented the research concerning novel biodegradable aliphatic PLA-co-PBS-co-PLA pairs in terms of chemical synthesis, structural and physical characterization, moreover, focused on PLLA-co-PBS-co-PLLA/ PDLA-co-PBS-co-PDLA mixture systems to form stereocomplexes, and studied the effects of bearing the diverse blocks length of PBS and PLLA/PDLA blocks. The second part concerned chemical synthesis and characterization novel PS-co-PLLA/PS-co-PDLA systems, and further research on the mechanism of stereocomplexes formation in non-selected solvent and the first explore the kinetics of stereocomplexation using the UV methods.1. New enantiomeric poly(lactide)-b-poly(burylenesuccinate)-b-poly(lactide)s: synthes es, characterization and in-situ self-assembly(l)To investigate the effects of co-polymerize PBS lengths to stereocomplexation of PLA blocks, a series of PLLA-co-PBS-co-PLLA/PDLA-co-PBS-co-PDLA copolymers weresynthesized with diverse lengths of PBS(Mi,,nmr=3.0 KDa~7.7 KDa) and a fixed length ofenantiomeric PLLA/PDLA building blocks(50 units). Their chemical structures, thermal and crystalline behavior were examined by means of 'HNMR, GPC, polarimeter, WAXD, DSC and TGA. Stereocomplexes of PLLA-co-PBS-co-PLLA/PDLA-co-PBS-co-PDLA were obtained from self-assembly in acetonitrile solution. The thermal and crystalline behaviors of stereocomplexes obtained from self-assembly in the solution were examined by DSC, TGA, WAXD.The stereocomplexes formation was also produced by chloroform volatilization, and it is characterized by DSC. Morphological studies were characterized by means of SEM for the stereocomplexes obtained by solvent volatilization from the chloroform solution.(2)In-situ self-assemblies of triblock PLLA-co-PBS-co-PLLA and PDLA-co-PBS-co-PDLA have been investigated in acetonitrile solution. At first two series ofPLLA-co-PBS-co-PLLA and PDLA-co-PBS-co-PDLA respectively denoted as the P and Q triblock copolyester series were prepared with fixed PBS block (Mn,NMR=6.9 KDa) and diverse enantiomeric PLLA/PDLA blocks. Further their chemical structures and thermal properties were characterized by means of titration, 'HNMR, GPC, polarimeter, WAXD, DSC and TGA.Moreover, morphological studies by scanning electron microscopy (SEM) indicated formation of disk or platelet-like microparticles. It was noted that diameters of the in-situ self-assembled microparticles decreased from 1.28-1.50 urn down to 480-660 nm through tailoring the enantiomeric PLA block length, and the other factors as achiral building block, enantiomeric block length and preparation conditions were suggested to play important roles in in-situ self-assembling these enantiomeric triblock copolyesters.2. Synthesis, Characterization of New Diblock Polystyrene-b-Poly(Iactide)s Bearing Enantiomeric Poly(lactide) Blocks and Their in-situ Self-assembly In SolutionTo investigate the effects of co-polymer to stereocomplexation of PLA blocks, two series of enantiomeric diblock PS-co-PLLA (LI, L2) and PS-co-PDLA (Dl, D2) with different enantiomeric PLA block populations were synthesized through strategy with a combination of 4-OH-TEMPO mediated radical polymerization of styrene and successive SnOct2 catalyzed ring-opening polymerization of individual enantiomeric l-/d- lactide monomers, and the diblock copolymers were further characterized. Subsequently, the in-situ self-assemblies of LI and Dl, and L2 and D2 mixture were studied in different solvents by means of DSC, NMR, WAXD, DLS, SEM and UV spectrometer with respect to the assembling dynamics and morphologies of organized structural hierarchies. As a result, a diblock structure dependence of in-situ assembly in non-selective and selective solvents will be discussed with a proposed mechanism.