Study On Novel Stimulated Resistant Binary Polymer System

Stimuli-responsive polymers with different functional groups belong to smart polymers that can afford large physicochemical changes upon minor environmental stimuli, resulting in the wide-range applications, such as nanotechnology, gene transfection and drug controlled release. The thesis mainly studied about pH and photo sensitive micellar behaviors and could be divided into three parts as follows.First:A three armed ATRP initiator C-Br3 containing coumarin group was designed and synthesized, which was used to prepare amphiphilic star polymer, C-(PDMAEMA80-b-PS8)3. The structures of C-Br3 and polymer were characterized by FT-IR, GPC,1H-NMR and UV-vis. Then the pH-induced behavior of polymer was studied, the normalized maximum emission, zeta potential and solution transmittance changes upon protonation provide some insight into the pH-induced behavior of polymer. The morphology changing phenomenon was successfully monitored by DLS and TEM measurements. It was shown that the Rh increased linearly as the pH value was decreased. In addition, polymers can self-assemble into three types of micelle morphologies in the aqueous solutions at various pH values, such as spherical micellar structures, spiky-shelled nanostructures and hollow loose micelles. Obviously, it can form the pH-induced accompanying outward movement of hydrophobic coumarin centers within the polymer micelles according to a stretched arrangement of the protonated PDMAEMA outer segments in the hydrophilic shell.Second:The photodimerization characteristics of anthracene pendants within amphiphilic polymer were researched. An amphiphilic polymer of PEO-b-PAM has been synthesized by ATRP, which can spontaneously form aggregated micelles in aqueous solution. Thus, anthracene pendants would be entangled into the confined micelle core with high local concentration and restricted mobility, which may facilitate the dimerization. The UV-vis spectrum of polymer showed a series of vibrationally spaced absorption structures at 320,338,353,371 and 392 nm (ringer like absorption bands). During irradiation, anthracenes can undergo [4+4] cycloaddition reaction and all the absorbance bands decreased significantly. Then the photodimerization kinetics can be monitored by UV-vis measurement and an adjustable double grating monochromator was used to afford the narrow band wavelength of light in the UV-vis-NIR region. It shows that the obtained time dependences of PD are fit very well to the biexponential eqn of PD=X1(1-e-k1t)+X2(1-e-k2t). Note that the sum of X1 and X2 determines the maximum photodimerization extent that the anthracene could reach after sufficient irradiation time, which is independent of light intensities. All the X1+X2 values obtained by the UV light irradiations were above 90%. While the PDmax values obtained by the vis-NIR light irradiations only reached the half of the UV light irradiations. This indicates that anthracenes cannot afford the similar photodimerization efficiencies of UV light by simply strengthening the power of vis-NIR light.Third:equilibrating immigration and anthracene-maleimide-based Diels-Alder-trapping of octylmaleimide in mixed photocross-linked polymer micelles. Two water soluble amphiphilic random copolymers of PAV and PAA containing coumarin and anthracene pendants, i.e. P(AMPS-co-VBC) and P(AMPS-co-AM), were designed and synthesized by radical polymerization. They were independently dissolved in water and photo-crosslinked using 365 nm LED light to a certain crosslinking degree, resulting in photo-crosslinked polymer micelles of PAV85% and PAA66%. The fluorescence quencher of noctylmaleimide (OM) was chosen as hydrophobic guest to be uploaded into PAV 85% polymer micelles. Then OM/PAV 85% was chosen as a maleimide source to mix with PAA 66% to form the mixed micellar systems. The equilibrating immigration of OM molecules from PAV85% into PAA66% polymer micelles was investigated using the emission spectra techniques. Furthermore, when the mixed system was heated to high temperature, the OM molecules would be trapped by PAA66% polymer micelles because of the thermal-induced anthracene-maleimide Diels-Alder addition.