Synthesis And Chatacterization Of Polymeric Nanoparticle By Ring-Opening Metathesis Polymerization

Polymeric core-shell nanoparticles with special structure and some novel physical and chemical properties have attracted considerable research interest because of their promising applications in the fields of drug delivery and release, phase transfer, preparation of nanomaterials, catalysis, nanocomposites, and lithography, etc. First, ring-opening metathesis polymerization (ROMP) of 2,3-bis(2-bromoisobutyryloxymethyl)-5-norbornene (BNBE) was carried out in toluene to yield a living homopolymer PBNBE for a constant reaction time. After that, the second monomer 7-oxanorborn-5-ene-exo-exo-2,3-dicarboxylic acid dimethyl ester (ONBDM) was added to this living PBNBE macrospecies and stirred for an additional polymerization time resulting in the formation of the block copolymer. Because the PBNBE block of the copolymer is soluble while PONBDM block is insoluble in this solution, the micelles composed of a densely packed core of the PONBDM blocks and the shell of PBNBE blocks were synthesized by the polymerization-induced self-assembly. The effect of the concentration and the feed molar ratios of the monomers upon the synthesis of the micelles were also investigated. The results of NMR analysis showed that the molecular weights and the compositions of the block copolymers were well controlled by the feed molar ratios of monomers. The polymeric micelles were confirmed by the dynamic light scattering (DLS) technique and showed the hydrodynamic diameter (Dh) of polymeric micelles increased by extending the length of PBNBE blocks but decreased with increasing the length of PONBDM blocks. The obtained polymeric nanoparticles were found to be stable in several days or longer and redisperseable in toluene. The morphologies of the aggregates were revealed to be spherical by atom force microscopy (AFM) and transmission electron microscopy (TEM) measurements.Furthermore, the polymeric hollow nanoparticles were synthesized through ROMP, atom transfer radical polymerization (ATRP), ring-closing metathesis (RCM), and core etching. First, the copolymers were synthesized via ROMP by sequential adding monomers, first ONBDM, then norbornene (NBE) and BNBE in CHCl3. Second, the ATRP of 4-butenyl-styrene (BS) was carried out by using PONBDM-b-PNBE-b-PBNBE as macroinitiator and CuBr/PMDETA as catalyst/ligand at 110℃for constant reaction time in chlorobenzene. Besides, because the polymer can self-assemble spontaneously in toluene to form polymeric micelles, the cross-linked micelles were synthesized by RCM using Ru-I in toluene. At last, the hollow micelles were synthesized though core etching. The molecular weights and the compositions of the block copolymers were characterized by NMR, GPC and elemental analysis (EA). The micellar characteristics of the copolymers were investigated by using DLS, AFM and TEM measurements. The hollow spherical morphologies with diameter from 100 nm were obtained.