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A novel one-step method has been developed to synthesize organically modified layered double hydroxide under ambient condition and without requirement of carbonate-free condition. This method has been found to be effective in the presence of several competitive anions and provides modified products with improved homogeneity, crystallinity, etc., as compared to other commonly known methods such as anion exchange and regeneration. The critical control of the pH value of the reaction medium is a key aspect of this method and provides a high degree of intercalation of the surfactant without forming any pure LDH phase. WAXS and FTIR analysis prove the homogeneous nature of the modified LDH. In contrast to the regeneration method, the chemical environment of the metal hydroxide layers remains identical to that of the unmodified LDH, as confirmed from the solid-state 27Al MAS NMR spectroscopy.

The synthesis of highly regioregular and alternating polythiocarbonates from carbon disulfide and terminal epoxides has been achieved. The copolymerizations were performed under ambient and solvent-free conditions in the presence of LiO t Bu (0.125−0.5 mol %) as initiator. At higher loadings the reaction pathway switched in favor to the catalytic formation of cyclic dithiocarbonates. Under optimized reaction conditions polymers with molecular weights up to 109 kg mol −1 were isolated. The NMR spectroscopic analysis of the polythiocarbonates revealed that 94% of backbone structure is formed by strongly alternating head-to-head arrangement of epoxypropane and 1,2-epoxybutane monomers, respectively, at a thiocarbonate group −CHR−OC(S)O−CHR− and tail-to-tail arrangement at a trithiocarbonate group −CH 2 −SC(S)S−CH 2 −. Atactic polymers were obtained using racemic mixtures of the epoxides, but an isotactic polymer was obtained when chiral (R)-epoxypropane was converted. A mechanism is proposed which rationalizes the regio-and stereochemistry observed for the alkoxide-initiated copolymerization of CS 2 and terminal epoxides.

Sequential copolymerizations of trimethylene carbonate (TMC) and l-lactide (LLA) were performed with 2,2-dibutyl-2-stanna-1,3-oxepane as a bifunctional cyclic initiator. The block lengths were varied via the monomer/initiator and via the TMC/l-lactide ratio. The cyclic triblock copolymers were transformed in situ into multiblock copolymers by ring-opening polycondensation with sebacoyl chloride. The chemical compositions of the block copolymers were determined from (1)H NMR spectra. The formation of multiblock structures and the absence of transesterification were proven by (13)C NMR spectroscopy. Differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), and dynamic mechanical analysis (DMA) measurements confirmed the existence of a microphase-separated structure in the multiblock copolymers consisting of a crystalline phase of poly(LLA) blocks and an amorphous phase formed by the poly(TMC) blocks. Stress-strain measurements showed the elastomeric character of these biodegradable multiblock copolymers, particularly in copolymers having epsilon-caprolactone as comonomer in the poly(TMC) blocks.

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