To mimic the three-dimensional (3-D) globular architecture resulting from the precise positioning of hydrophobic/hydrophilic domains (blocks) of naturally occurring proteins, water-soluble linear and star homopolymers of N,N'-dimethylacrylamide (DMA) were synthesized with prescribed molecular weights via reversible addition-fragmentation chain transfer (RAFT) polymerization and subsequently used as macro chain transfer agents for block copolymerization with N-isopropylacrylamide (NIPAM). For the star block copolymers, the interior block consisted of NIPAM while the exterior block was DMA. Since polyNIPAM thermally switches from hydrophilic to hydrophobic, the 3-D solution conformations of the polymers were studied as a function of temperature using differential scanning calorimetry (DSC), static light scattering (SLS), and dynamic light scattering (DLS). The polymers were observed to form monodisperse aggregates in an aqueous pH 4 buffer solution when heated above the lower critical solution temperature (LCST) of polyNIPAM. The temperature at which the polymers aggregated and the size of the aggregates were dependent on the NIPAM block length and the core architecture. A simple model based on an optimal area per headgroup was used to analyze our experimental findings and was useful for predicting the final size and molecular weight of the aggregates formed.

To a solution of 4-chlorobenzaldehyde oxime ( 0.40g) in CH2Cl2 (10 mL) in a large test-tube were added 1.0 mL of cycloheptene and 3 drops of triethylamine.[...]

To a solution of 4-chlorobenzaldehyde oxime (0.40g) in CH 2 Cl 2 (10 mL) in a large test-tube were added 1.0 mL of cyclododecene and 3 drops of triethylamine. The solution was cooled to 5°C, then 7.0 mL of 5% NaOCl solution in water was added in small portions. After each portion was added, the test-tube was agitated with a Vibromixer TM stirrer for 15 seconds. After the addition of all of the NaOCl solution, the test-tube was agitated with a Vibromixer TM stirrer for 15 seconds every 5 minutes over the next hour. The reaction mixture was allowed to stand at least overnight. The layers were separated, and the aqueous layer was extracted with CH 2 Cl 2 (5 mL). The combined CH 2 Cl 2 layers were evaporated to yield an off-white solid. The solid was recrystallized from 95% ethanol to yield shiny white flakes. Yield: 0.24g (29%).

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