SYNTHESIS AND SELF-ASSEMBLY OF DENDRONIZED-LINEAR AMPHIPHILIC BLOCK COPOLYMER

The monomer (DHEMA (G1)) was synthesized by esterification of the 2-hydroxyethyl methacrylate with acetonide protected 2, 2-bis (methylol) propionic acid, and then undergone the ATRP to give the macroinitiator PDHEMA(G1)-Br. By using PDHEMA (G1)-Br to initiate styrene, PDHEMA (G1)-b-PS block copolymer was prepared. Based on the PDHEMA(G1)-b-PS as reactive precursor, through iterative process of the deprotection of acetonide and dendronization by esterification with bis-MPA anhydride, the dendronized-linear amphiphilic block copolymers PDHEMA (Gn-OH)-b-PS (n = 2 similar to 3) were prepared, and the asymmetrical structure of designed copolymers was a combination of a hydrophilic multihydroxyl dendronized PDHEMA (Gn-OH) block and a hydrophobic linear PS block. The resultant copolymers were characterized by IR and H-1-NMR. The self-assembly morphology of PDHEMA(Gn-OH)-b-PS(n = 1 similar to 3) in the binary solvent mixture (DMF/CH3OH) was investigated with the copolymer concentration at 2 mg/mL. When the CH3OH content was at 50 wt%, PDHEMA (G1-OH)-b-PS, PDHEMA (G2-OH)-b-PS and PDHEMA (G3-OH)-b-PS self-assembled into spherical micelles with core-fringe structure. The diameter of micelles increased with increasing generation of dendronized blocks. For the copolymer PDHEMA (G3-OH)-b-PS, when the CH3OH content was at 66 wt%, the compound rodlike micelles containing branch and ring structure were formed and spherical micelles were also encountered occasionally. When the CH3OH content reached 75 wt%, only the compound rodlike micelles contaning branch and ring structure were observed. The unique morphological variety of muti-rings could be attributed to the coexistent effect of branch and ring during the development of rodlike micelles.