Synthesis Of PEGylated Brush-type Copolymers For A Plurality Of Plug-and-play Functions

Recently, hyperbranched polymers have caused extensive concerns and attentions because of multifunctional chains, and a variety of functional groups at the end of chains, which would be utilized for preparing expecting active reaction sites so as to synthesize multifunctional nanocomposite. There are two common types of copolymers, one is brush-type copolymer with multiple side chain, the other is hyperbranched dendritic macromolecules. The former is prepared by method of atom transfer radical polymerization(ATRP), which has many advantages, such as adapting to a wide range of monomers, good controllability, preparing copolymers with narrow molecular weight distribution, strong molecular design capability, it is used for preparing block copolymers containing PEG side chains after modification with different functional groups as a flexible plug-and-play platform. The latter is used for modifying the surface of GO with hydrophobic molecules to obtain amphiphilic materials, which could be used for anti-inflammatory. In this paper, based on the above two directions, we carry out the related research, specific work basically has the following two aspects:1. In the first work, it is aimed to develop a well-defined brush-type copolymer P(PEGMA-N3-co-PEGMEMA)-b-PMAA via atom-transfer radical polymerization(ATRP) technique, and further to demonstrate its a plurality of plug-and-play functions. The brush-type copolymer consists of three main parts:(i) poly(ethylene glycol) methacrylate(PEGMA);(ii) poly(ethylene glycol)methyl ether methacrylate(PEGMEMA), in which the hydroxyl groups in the pendants could be translated to azide ones through esterification;(iii) poly(meth acrylic acid)(PMAA), which was derived from poly(t-butyl methacrylate) via hydrolysis reaction. Each part offered the different functions. For example, the PEG side chains could stabilize nanoparticles due to their hydrophility, and the azide groups would provide the reactive sites for click chemistry, while the carboxyl groups could combine with positively-charged ions or molecules via electrostatic interaction. Chemical structures of the copolymers were characterized by 1H NMR and gel permeation chromatography. Subsequently, the self-assembly behavior of the copolymers and the micelles were investigated by dynamic light scattering, zeta potential and fluorescent spectroscopy, respectively. Finally, the copolymer solution was mixed with dopamine modified Fe3O4 nanoparticles(Fe3O4-DA) to form the stable and multifunctional Fe3O4 nanoparticles. This work provides a new strategy for preparation of multifunctional amphiphilic copolymer and magnetic nanoparticles.2. In the next work, the carboxyl groups were protected by tertiary butyl groups so the hydrophobic eighteen alkyl isocyanate(ODI) molecules were grafted onto the surface of a two-dimensional graphene oxide sheet, then the tertiary butyl groups were removed by hydrolysis of TFA, and the hydrophilic dendritic macromolecules(Dendrimer) were grafted onto the surface of the GO sheet to obtain amphiphilic graphene oxide derivatives, The hydrophobic drug molecules were loaded onto surface of graphene oxide sheet via methods of π-π stacking and the interaction between hydrophobic alkyl chains and hydrophobic drug molecules. The drug loading ratio of graphene oxide materials after modification were higher than that of graphene oxide without the modification. The drugs loading on the graphene oxide sheet were released by means of slow release and were utilized to investigate the effects of its anti-inflammatory. The drug molecules were used to cure inflammatory BV2 neural microglia cells to realize the target of anti-inflammatory treatment, which receiving good effect of anti-inflammatory treatment as a result. We have proved that the new type graphene oxide derivatives have broad applications and good prospects in fields of drug loading, biomedicine and multifunctional nanocomposites.