Self-assembly of poly(2-alkyl-2-oxazoline)s by crystallization in ethanol-water mixtures below the upper critical solution temperature.

Crystallization of poly(2-isobutyl-2-oxazoline) and poly(2-nonyl-2-oxazoline) is found to occur by room temperature annealing below the upper critical solution temperature in ethanol-water solvent mixtures. Both polymers produce similar self-assembled structures (see image), resembling the previously reported crystalline hierarchical structures obtained from hot aqueous poly(2-isopropyl-2-oxazoline) solutions above the lower critical solution temperature. These observations suggest that the crystallization induced self-assembly process is a rather general phenomenon occurring for semicrystalline polymers in liquid-liquid two phase systems.

Universal polymer analysis by (1)H NMR using complementary trimethylsilyl end groups.

New degenerative chain transfer agents, namely 4-(trimethylsilyl)benzyl 4'-(trimethylsilyl)butane-dithioate, 4-(trimethylsilyl)benzyl 3'-(trimethylsilyl)propyl trithiocarbonate and their 3-(trimethylsilyl)benzyl isomers, that are two-fold labeled with complementary trimethylsilyl (TMS) markers, were designed and shown to be powerful tools for universal polymer analysis by conventional (1)H NMR spectroscopy. Their use in controlled free radical polymerization, here the reversible addition-fragmentation chain transfer (RAFT) method, resulted in polymers with low polydispersities up to high molar masses, as well as with defined complementary TMS end groups. Thus, routine (1)H NMR spectra allowed facile determination of the molar masses of polymers of various chemical structures up to at least 10(5) g/mol, and simultaneously provided crucial information about the content of end groups that is typically >95% when polymerizations are correctly performed.