Studies On The Solution Behavior Of Graft Copolymers And Their Applications As Dispersants, And Gene Delivery Carriers

Amphiphilic polymers have attracted much attention in the past because of their special aggregating behavior in bulk, selected solvents and surfaces. Normally, there are two different kinds of polymeric chains co-existed in amphiphilic polymer structures, which show different affinity to the two different phases (e.g. water and oil, two kinds of oils or solids with different characters). In this thesis, we focused on graft acrylic polymers (one of the widely industrial utilized amphiphilic polymers), which were copolymerized by CCTP (catalytic chain transfer polymerization)-synthesized macromonomer and nomal acrylic monomers. Moreover, the solution behavior of amphiphilic graft polymers and the influence of small surfactants (Cetyltrimethylammonium bromide (CTAB), or Sodium dodecyl sulfate (SDS)) have also been studied systematically. And the graft polymers with proper structures were applicated as dispersants to stabilize carbon black (CB) particles in xylene or water. Besides, graft polycations were synthesized via the aminolysis reaction between oligoamines and CCTP macromonomer; and the cytotoxicity, ability for complexeing with plasmid DNA and efficiency for in vitro transfection of the polycations were evaluated.(1) The anionic amphiphilic graft polymer (the main chain is hydrophobic and the side chain is hydrophilic) was prepared via CCTP method. Surface tension study indicates that the amphiphilic graft polymer has no evident critical micelle concentration (CMC). Dynamic light scattering (DLS) and transmission electron microscope (TEM) results reveal that even at extremely low concentration, there are aggregates existed in the amphiphilic polymer solution. In addition, the interactions between the anionic polymer and cationic surfactant CTAB and anionic surfactant SDS were studied. The data shown that the anionic amphiphilic polymer could interact with CTAB forming compact complexes; the size and Zeta potential of the complexes was dependent on the CTAB concentration. The interaction between the polymer and CTAB is mainly anionic-cationic electrostatic attractions. In the system of amphiphilic polymer/SDS, the studies revealed that although strong electrostatic repulsions were existed between both of them, the amphiphilic polymer could still interact with SDS by hydrophobic attractions which are originated from the hydrophobic chains of the polymer and SDS.(2) Three kinds of oil-soluble graft polymers (containing carboxylic, amino and quaternary ammonium groups in the main chain respectively) were synthesized via the similar synthetic route, and the influences of the functional groups on the abilities of the polymers to disperse CB in xylene were evaluated. The results indicate that the content of the functions in the main chain has great influence on the CB dispersion; and the polymers containing amino groups in the main chain show better CB dispersing ability than the ones containing carboxylic groups. When the amino groups were quaternized, the dispersing ability of the polymer is improved remarkably and is similar to the commercial dispersant Disperbyk-163.(3) Several amphiphilic polymers were designed and synthesized. The influences of the hydrophobic backbone components, the length of the backbone, the lateral chain and the content of functional groups on the CB dispersion were studied. The results indicate that the amino groups and proper contents of phenyl groups in the backbone of the amphiphilic polymer were favored for the dispersing of CB in water. Besides, polymer concentration, ion strength and pH have great influence on CB dispersion. When electrolyte is existed in the system, or the solution is acidic, CB could not be dispersed effectively. The CB dispersing ability of the optimal polymer dispersant can be equal to the commercial dispersant Disperbyk-190.(4) Acrylic polycations were prepared via the aminolysis reaction between oligo amines and ester of PMMA. The complex capability of the polycations with plasmid DNA was evaluated by Agarose Gel Retardation Assay, TEM, DLS and Zeta potential measurements. The results indicate that all of the polycations could condense DNA compactly and form regular nanospheres. The size of the complexes is about 200nm, while the Zeta potential of the complexes is over 20mV. The results of cytotoxicity in HEK293T and HeLa cells indicate that the cytotoxicity of polyctions is much lower than that of 25 kDa PEI, and the cytotoxicity of 25 kDa PEI is 100 orders of magnitude higher than that of PMMA-g-oligoamines. The results of in vitro transfection exhibit that all of the three polycations could transfer the plasmid DNA to HEK293T and HeLa cells effectively, and the transfection efficiency is comparable to that of 25 kDa PEI. The confocal results indicate that all of the three polycations could transfer the plasmid DNA to nucleolus effectively.