Phase diagram of star-shaped polystyrene/cyclohexane system: location of critical point and profile of coexistence curve

Highly branched thermoresponsive polysaccharide derivative in water. Partly substituted highly branched cyclic dextrin ethylcarbamate

A thermoresponsive highly branched polysaccharide derivative was revealed from commercially available highly branched cyclic dextrin (HBCD), originally synthesized from amylopectin. Eight samples of partially substituted ethyl carbamate derivatives of HBCD (HEC) were prepared with a degree of substitution DS ranging from 0.27 to 1.46. Three samples with DS = 0.88, 1.05, and 1.22 showed LCST type phase separation in water. The intrinsic viscosity and form factor in water were typical of the hyperbranched structure. The intermolecular interactions between HEC and iodine or 1-anilinonaphthalene-8-sulfonic acid (ANS) were appreciably different from those of the linear analog (AEC), suggesting that the locally bent helical conformation of highly branched HEC chains has a different interaction with small molecules. The phase diagram of HEC-water systems was accidentally similar to that of the linear chain with the same molar mass and DS, although the one phase region of the branched polymer chain-poor solvent system is usually wider than that of the corresponding linear chain. This is likely due to the lower hydration nature of the polymer segment of HEC chains than that of the corresponding linear chain.

Solution characterization of a hyperbranched polysaccharide carbamate derivative and specific phase separation behavior due to chain branching

A hyperbranched polymer consisting of rigid helical part chains was prepared as highly branched cyclic dextrin tris(phenylcarbamate) (HTPC) with the weight-average molar masses of 880 and 590 kg mol-1. Small-angle X-ray scattering (SAXS) measurement and viscometry were performed on the samples in good and poor solvents to determine the dimensional and hydrodynamic properties in solution. The HTPC molecule has a much more compact conformation than the linear chain with the same molar mass as expected for the hyperbranched architecture. While the corresponding linear polymer is soluble in methyl acetate (MEA) over a wide temperature range, HTPC is only soluble in the solvent at low temperatures. A typical LCST-type phase diagram was observed for the HTPC-MEA system, indicating that the interactions between the polymer segment of HTPC and the MEA molecules are substantially different from those of the linear chains. This is most likely due to the bending helical chains near the branching point of HTPC having different interactions with solvent molecules.

Nonionic star polymers with upper critical solution temperature in aqueous solutions

Novel UCST star poly(2-ureido methacrylates) synthesized via the ARGET ATRP technique showed enhanced trapping abilities of model drug molecules.