Physical Characterization of Arborescent Polystyrene

The influence of polymer architecture on intermolecular interactions in dilute solutions was investigated by membrane osmometry in toluene (good solvent for polystyrene), cyclohexane (theta or 0 solvent), and methylcyclohexane (poor solvent Striolo et al., 2001). The osmotic second virial coefficient (B22) measured for arborescent polystyrene in toluene was lower than for homologous linear polymers, as expected due to their smaller Rg. In a 0 solvent (cyclohexane), branching lowered the 0 temperature from 34.5 °C (linear homolog) to 32.2 °C (GO polymer). The 0 temperature for the GO polystyrene sample in methylcyclohexane was likewise lowered to 36 °C, as compared to values estimated between 60 and 70 °C for linear polystyrene samples. The experimental osmotic pressure data were successfully fitted with a molecular-thermodynamic equation suitable for colloids, indicating that the behavior of arborescent polystyrene molecules in dilute solution corresponds to a perturbed (weakly interacting or interpenetrable) hard sphere. 

1 Physical Characterization of Arborescent Polystyrene-graft-Poly(2-vinylpyridine) 

The amphiphilic character and the covalently bonded, stable structure of the PS-gra/f-P2VP copolymers is particularly interesting for applications as unimolecular micelles in the solubilization of hydrophobic compounds in aqueous environments, and the sustained release 

The results discussed above show that arborescent PS-grq/it-P2VP copolymers can be designed to solubilize or release hydrophobic compounds of different polarities at controllable rates. 

4 Arborescent Polystyrene-graft-Polystyrene-block-Poly(2-vinylpyridine) 

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