The sequential living polymerization of N-silylphosphoranimines for the synthesis of polyphosphazene-b-polyphosphazene diblock copolymers (PP-b-PP) has been studied both experimentally and theoretically. For the experiments, BrMe 2 PN−SiMe 3 , [Cl 3 PNPCl 3 ][X] (X = PCl 6 − , Cl − ), Cl 3 PN−SiMe 3 , ClMe 2 PN−SiMe 3 , and [Me 3 PNPMe 2 Cl] + were used as representative model reagents. Density functional theory (DFT) calculations in the gas phase adjusted for solvent effects on ClMe 2 PN− SiMe 3 , [Cl 3 PNPCl 3 ] + , Cl 3 PN−SiMe 3 , and ClMe 2 PN−SiMe 3 confirmed the experimental observations. The results have shown the necessity of starting with monoend-capped initiators to avoid the formation of triblock chains. It was also demonstrated that the nature of the nucleophilic N-silylphosphoranimines and the electrophilic cationic end groups of the living polyphosphazenes strongly affects the polymerization reaction, imposing limits to its synthetic potential. Thus, good electron donor N-silylphosphoranimines, i.e. XR 2 PN−SiMe 3 , react better with electron-deficient cationic end groups such as N−PCl 3 + , probably by molecular orbital (MO) control. The results led to the designed synthesis of well-defined PP-b-PP block copolymers with narrow molecular weight distributions of formula [N P(Ph)(Me)] n -b-[NP(OCH 2 CF 3 ) 2 ] m and [NP(Ph)(Me)] n -b-[NP(O 2 C 12 H 8 )] m , which are excellent candidates for micellation studies.
a b s t r a c tUnprecedented polyurethanes with rigid spiroacetal linkages in the backbone were synthesized from renewable resource compounds. First, the large-scale synthesis of a rigid diol monomer containing acetal bonds was established. Subsequently, this diol monomer was combined with seven different diisocyanates to vary the backbone of thermoplastic polyurethanes, leading to a spectrum of chemical and physical properties. The molar masses of the polymers ranged from 8 to 45 kDa and the corresponding polymers were obtained in high yields. DSC and DMTA analysis demonstrated glass transition temperatures up to 85°C. Acid-mediated degradation of the materials was not noticed during hydrolytic stability tests.
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