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Poly(2-isopropenyl-2-oxazoline) (PIPOx) has drawn significant attention for numerous applications. However, the successful living anionic polymerization of 2-isopropenyl-2-oxazoline has not been reported previously. Herein, we describe how well-defined PIPOx with quantitative yields, controlled molecular weights from 6800 to over 100,000 g/mol and low polydispersity indices (PDI ≤ 1.17) were synthesized successfully via living anionic polymerization using diphenylmethylpotassium/diethylzinc (DPM-K/Et2Zn) in tetrahydrofuran (THF) at 0 °C. In particular, we report the precise synthesis of well-defined PIPOx with the highest molecular weight ever reported (over 100,000 g/mol) and low PDI of 1.17. The resulting polymers were characterized by ¹H and 13C nuclear magnetic resonance spectroscopy (NMR) along with size exclusion chromatography (SEC). Additionally, the reactivity of living PIPOx was investigated by crossover block copolymerization with styrene (St), 2-vinylpyridine (2VP), and methyl methacrylate (MMA). It was found that the nucleophilicity of living PIPOx is of this order: living PS > living P2VP > living PMMA > living PIPOx. The self-assembly behavior in bulk of PIPOx-b-PS-b-PIPOx triblock copolymers having different block ratios of 10:80:10 and 25:50:25 was studied using transmission electron microscopy (TEM). The formation of spherical and lamellar nanostructures, respectively, was observed. [ABSTRACT FROM AUTHOR]

The deuterated homopolymers and their corresponding polystyrene-block-polybutadiene and polystyrene-block-polyisoprene copolymers require lower cloud pressures than their hydrogenous analogues to dissolve in a compressible alkane solvent, such as propane. For symmetric diblocks, deuteration reduces the micellization pressure. By contrast, for asymmetric diblocks with a long diene block relative to the styrene block, deuteration can increase the micellization pressure. All in all, however, the deuteration effects, while measurable, do not qualitatively change the principal diblock properties in compressible propane solutions, such as pressure-induced micelle decomposition, micelle formation and micelle size, and their temperature dependence. Therefore, isotope labeling should be a useful approach to neutron-scattering characterization for styrene-diene block copolymers in compressible alkane systems. [ABSTRACT FROM AUTHOR]

Micellar solutions of polystyrene-block-polybutadiene and polystyrene-block-polyisoprene in propane are found to exhibit significantly lower cloud pressures than the corresponding hypothetical nonmicellar solutions. Such a cloud-pressure reduction indicates the extent to which micelle formation enhances the apparent diblock solubility in near-critical and hence compressible propane. Concentration-dependent pressure−temperature points beyond which no micelles can be formed, referred to as the micellization end points, are found to depend on the block type, size, and ratio. The cloud-pressure reduction and the micellization end point measured for styrene−diene diblocks in propane should be characteristic of all amphiphilic diblock copolymer solutions that form micelles in compressible solvents. [ABSTRACT FROM AUTHOR]

The structures and association properties of thermosensitive block copolymers of poly(methoxyoligo(ethylene glycol) norbornenyl esters) in D 2O were investigated by small angle neutron scattering (SANS). Each block is a comblike polymer with a polynorbornene (PNB) backbone and oligo ethylene glycol (OEG) side chains (one side chain per NB repeat unit). The chemical formula of the block copolymer is (OEG 3NB) 79−(OEG 6.6NB) 67, where subscripts represent the degree of polymerization (DP) of OEG and NB in each block. The polymer concentration was fixed at 2.0 wt % and the structural changes were investigated over a temperature range between 25 and 68 °C. It was found that at room temperature polymers associate to form micelles with a spherical core formed by the block (OEG 3NB) 79and corona formed by the block (OEG 6.6NB) 67and that the shape of the polymer in the corona could be described by the form factor of rigid cylinders. At elevated temperatures, the aggregation number increased and the micelles became more compact. At temperatures around the cloud point temperature (CPT) T= 60 °C a correlation peak started to appear and became pronounced at 68 °C due to the formation of a partially ordered structure with a correlation length ∼349 Å. [ABSTRACT FROM AUTHOR]