Association behavior of polyisoprenes having cholesterol and phosphatidylcholine analogous end groupsK. Kostakis, S. Mourmouris, D. Charalabidis and M. Pitsikalis
Department of Chemistry, University of Athens, Panepistimiopolis Zografou, 15771 Athens, Greece email@example.com
(Received 29 April 2002 and Received in final form 13 November 2002 Published online: 11 March 2003 )
Linear polyisoprenes having dimethylamine end groups were prepared by high vacuum anionic polymerization techniques using 3-dimethylaminopropyllithium as the initiator. The amine group was reacted with 2-cholesteryl-2-oxo-1,3,2-dioxaphospholane to provide polymer chains having end zwitterionic groups chemically connected with cholesterol. The association behavior of these end-functionalized polymers was studied in cyclohexane by low angle laser light scattering, dynamic light scattering, and viscometry. The aggregation numbers, were found to decrease by increasing the molecular weight of the precursor polymer, due to excluded volume repulsions. The ability of cholesterol to form liquid crystal mesophases facilitated the association process leading to higher values. The hydrodynamic behavior of the aggregates was similar to that of star polymers. The dependence of the values on the molecular weight of the base polymer, the polydispersity of the associates and the absence of critical micelle concentration, cmc are compatible with the linear head-packing model.
82.30.Nr - Association, addition, insertion, cluster formation.
61.30.Vx - Polymer liquid crystals.
82.35.-x - Polymers: properties; reactions; polymerization .
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003