Preparation And Properties Of Thermosensitive Fluorinated Block Polymer By RAFT Polymerization

Amphiphilic block polymers can form aggregates with different shapes and cavity structures under certain conditions,which have good application prospects in drug encapsulation,controlled release and other fields.A series of temperature-sensitive amphiphilicfluoroblockpolymersPNIPAM-PHFBA-PNIPAM,PNIPAM-PBA-PNIPAM and PNIPAM-PTFEMA-PNIPAM were synthesized by reversible addition-fragmentation chain transfer?RAFT?polymerization,using N-isopropylacrylamide?NIPAM?as the hydrophilic monomer,hexafluorobutyl acrylate?HFBA?,butyl acrylate?BA?and trifluoroethyl methacrylate?TFEMA?as hydrophobic monomers,S,S'-bis??,?'-dimethylacetic acid?trithiocarbonate?TTC?as the chain transfer agent and azobisisobutyronitrile?AIBN?as the initiator.Hydrophilic block PNIPAM had temperature sensitivity and could respond well to temperature change.Hydrophobic block was a kind of fluoropolymer with excellent microphase separation structure.So the synthesized polymers could self assemble into micelles in selective solvent.The temperature sensitivity and self-assembly properties of the synthesized polymers were measured by transmittance,surface tension and dynamic laser light scattering.Sudan IV was used as a model drug to study the loading capacity of polymer micelles to hydrophobic drugs,so as to explore the application prospect of polymers in biomaterials.1.The temperature sensitivity of the fluoro block polymer PNIPAM-PHFBA-PNIPAM and the fluoro free block polymer PNIPAM-PBA-PNIPAM were studied.The results showed that different polymers had good temperature sensitivity and reversible temperature sensitivity,and the response of fluoro block polymers to temperature change were more sensitive than that of fluoro free block polymer.2.The effects of inorganic salts solution on the temperature sensitivity of fluorinated block polymer PNIPAM-PHFBA-PNIPAM were studied.The results showed that the LCST value of polymer solution had no obvious change in different concentrations of NaCl and CaCl₂,which indicated that the synthesized polymers had good salt resistance to Cl^-.In different concentrations of NaBr and KBr,the LCST value of polymers decreased slightly with the increase of solution concentration.3.The surface activity of fluorine-containing block polymer PNIPAM-PHFBA-PNIPAM and fluorine-free block polymer PNIPAM-PBA-PNIPAM were studied by surface tension method.The results showed that both of them had good surface activity and could form uniform and stable micelles at low concentration.The CMC values of fluorine-containing block polymers were lower than that of fluorine-free block polymers,which indicated that the introduction of fluorine-containing hydrophobic monomers made the polymer more prone to micro phase separation and stronger micellization ability.4.The particle size and size distribution of polymer PNIPAM-PHFBA-PNIPAM solution were measured by dynamic laser light scattering,and the morphology of polymer micelles were observed by scanning electron microscope.The results showed that when the temperature was lower than LCST,the particle size of polymer micelles was uniform and stable.When the temperature was higher than LCST,the aggregation of polymer micelles resulted in the increase of particle size.5.The temperature sensitivity and surface activity of fluorinated block polymers PNIPAM-PTFEMA-PNIPAM were studied and compared with PNIPAM-PHFBA-PNIPAM.The results showed that the LCST values of PNIPAM-PTFEMA-PNIPAM were slightly higher than that of PNIPAM-PHFBA-PNIPAM,indicating that the higher the fluorine content in the block polymer,the stronger the hydrophobicity and the lower the LCST value.The CMC of PNIPAM-PTFEMA-PNIPAM was slightly higher than that of PNIPAM-PHFBA-PNIPAM,indicating that the higher the fluorine content in the block polymer,the lower the critical micelle concentration,and the stronger the self-assembly ability of the polymer to form micelles.6.Sudan IV was used as a model drug to study the drug loading properties of PNIPAM-PHFBA-PNIPAM and PNIPAM-PBA-PNIPAM micelles.The results showed that the micelles with different block ratios had good drug loading properties.