Arborescent polymers polystyrene

Puskas, J.E. et al. Synthesis and characterization of novel dendritic (arborescent) polyisobutylene-polystyrene thermoplastic elastomers, J. Polym. Set A, 43, 1811, 2005. 

Kwon, Y., Antony, P., Paulo, C., and Puskas, J.E. Arborescent polyisobutylene-polystyrene block copolymers—a new class of thermoplastic elastomers, Polym. Prepr., 43, 266-267, 2002. 

Winter, H.H. Evolution of rheology during chemical gelation. Prog. Colloid Polym. Scl,15,104—110,1987. Hempenius, M.A. et al. Melt rheology of arborescent graft polystyrenes. Macromolecules, 31, 2299, 1998. 

Puskas, J.E. Dendritic (arborescent) pol3tisobutylene-polystyrene block copolymers DMTA analysis and swelling studies, Polym. Mater. Sci. Eng., 91, 875-876, 2004. 

For the subsequent generation of arborescent graft polystyrenes, a dramatic increase in rj0 was observed by Hempenius et al. [43] for each of the three series included in their study. However, despite this increase in viscosity, the rj0 for each of these is still lower than that of the linear homologue polystyrenes of the same overall molecular weight. This jump in viscosity is due to an increase in branch density which in turn results in increase in chain extension similar to that observed by Roovers [31] for highly branched star polymers. 

This chapter focuses on the latest efforts in our laboratory aimed at the synthesis and the physical characterization of arborescent polymers. The synthesis of arborescent styrene and isoprene homopolymers is discussed, together with copolymers incorporating a polystyrene substrate grafted with side chains of different compositions such as poly(2-vinylpyridine). 

The step-wise synthesis of arborescent polymers, while able to generate large amounts of materials in good yield, requires isolation and purification of the crude product prior to substrate functionalization. For less-demanding applications not requiring stringent removal of the linear polymer contaminant, a one-pot method was recently developed by Yuan and Gauthier (2006) for the synthesis of arborescent polystyrene without isolation of the reaction intermediates. 

Kwon Y, Antony P, Paulo C and Puskas J E (2002) Arborescent polyisobutylene-polystyrene block copolymers - A new class of thermoplastic elastomers, Polym Prepr ACS 43 266-267. 

Puskas, J.E. Biomacromolecular engineering Design, S3mthesis and characterization. One-pot synthesis of block copolymers of arborescent polyisobutylene and polystyrene, Polym. Adv. TechnoL, 7, 1, 2006. 

Monolayers of arborescent polystyrenes have been investigated by scanning force microscopy [90]. Dense polymers with a small branch spacing (Mb 500 D) are nearly spherical and become more spherical on annealing, thereby causing the break-up of the film. On the other hand less densely branched polymers... 

Characterization data for two series of arborescent polystyrene samples based on the acetylation path are provided in Table 6.1 as an example (Li and Gauthier, 2001). The polymers were synthesized from either 5000 (PS5) or M 30 000 (PS30) 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. 

Figure 6.3 Release profiles for (a) indomethacin and (b) lidocaine in 0.05M HCl in the free state ( ) and from GlPS- ra/ -P2VP copolymer ( ). Mt is the cumulative mass released at time t, and Mgq is the mass released at equilibrium. (Reprinted from Polymer, 49, G.N. Njikang, M. Gauthier and J. Li, Sustained release properties of arborescent polystyrene-grq/it-poly (2-vinylpyridine) copolymers, 5474-5481, 2008, with permission from Elsevier.)...

Yun, S., Briber, R.M., Kee, R.A., and Gauthier, M. (2003) SmaU-angle neutron scattering of arborescent polystyrene-grayt-poly(2-vinylpyridine) copolymers. Polymer, 44,6579-6787. 

Lieu, J.G., Prausnitz, J.M., and Gauthier, M. (2000) Vapor-liquid equilibria for binary solutions of arborescent and linear polystyrenes. Polymer, 41,219-224. 

Munam, A. and Gauthier, M. (2008) Large-scale synthesis of arborescent polystyrenes. Journal of Polymer Science, Part A Polymer Chemistry, 46,5742-5751. 

Njikang, G., Gauthier, M., and Li, J. (2008c) Arborescent polystyrene-grq -poly(2-vinylpyridine) copolymers as unimolecular micelles. Solubilization studies. Polymer, 49,1276-1284. 

Striolo, A., Prausnitz, J.M., Bertucco, A. et al (2001) Dilute-solution properties of arborescent polystyrenes Further evidence for perturbed-hard-sphere behavior. Polymer, 42,2579-2584. 

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