Macromolecular Non-covalently Connected Micelles In Aqueous Media Self-assembled By P(AA-co-St)/PVP

In this paper, A series of amphiphilic random copolymers P(AA-co-St) with different monomer ratio were synthesized by free radical copolymerization in the solution of dioxane, using AIBN as initiator. The copolymers were characterized by means of infrared spectrum(IR),gel permeation chromatography(GPC),differential scanning calorimetry(DSC) and nuclear magnetic resonance(NMR).The synthesized P(AA-co-St) were assembled with polyvinylpyrrolidone(PVP) into micelles in aqueous media. Dynamic light scattering (DLS) was used to study the micellization of the system. The morphology of micelles were characterized by TEM. The results of DLS showed that hydrodynamic radiuses of micelles rised with increasing initial concentrations of P(AA-co-St) and PVP and molecular weight of PVP while rising with reducing contents of AA. When the concentration of P(AA-co-St) is low, AA content of P(AA-co-St) and molecular weight of PVP had a slight effect on the size of micelles. When the concentration of P(AA-co-St) is high, AA content of P(AA-co-St) and molecular weight of PVP had a significant effect on the size of micelles. The size of micelles was affected by several fctors. Different adding speed in the micellization could induce different size of micelles. Hdrodynamic radiuses of micelles reduced from 116 nm to 40 nm with increasing pH from 1.05 to 10.77 and increased from 56 nm to 110 nm with increasesing of NaCl concentration from 0.1 mmoL/L to 2.5 mmoL/L. The size of micelles reduced from 57.26 nm to 52.95 nm after dialysed. The results of TEM showed that micelles were regular spheres which had a fuscous nucleus and a tint shell. After stained by RuO4, the micelles could more clearly show the structure of nucleus and shell. Whats more, the staining time of RuO4 had a effect on observing the clear structure.The microenvironment of the micelles formed by P(AA-co-St) and PVP was studied by fluorescence spectrophotometer and UV spectrum. The results showed that the intensity of Pyrene emission spectrum increased and I1(the intensity of fluorescence in 374 nm)/I3(the intensity of fluorescence in 385 nm) reduced with increasing of concentration of P(AA-co-St) which indicated that polarity of microenvironment in micelles was more and more small and the structure of micelles was more and more compact. With increasing of concentration of P(AA-co-St),loading capacity of Pyrene in micelles increased. On the loading efficiency, the system with the lowest concentration of P(AA-co-St) had the highest loading efficiency.TEM was used to study the effect of SDS and CTAB on the morphology of micelles formed by P(AA-co-St) and PVP. The results showed that the effect of surfactant on morphology of micelles was not only related to its concentration, but also to the kinds and structure of surfactant. 10 mmol/LSDS could change morphology of micelles to shuttle aggregates with axis length about 200 nm and radial length about 40 nm. Necklace aggregates were formed when concentration of SDS was 240 mmol/L. Adding10 mmol/L CTAB, rod aggregates which were regular shape with axis length about 200 nm and radial length about 20 nm were formed.