Synthesis,Fluorescent And Catalytic Properties Of PNIPAM-based Thermosensitive Nanocomposites

The thermo-responsive block copolymers as novel intelligent materials have been widely used in many fields such as drug release,fluorescent probe and sensors,in which research focus is the polymers based on poly N-isopropyl acrylamide?PNIPAM?.In the article,PNIPAM-based nanocomposites were synthesized and utilized in sensing and catalytic applications.The main contents are as followed:1.Using 4-Cyano-4-?thiobenzoyl?sulfanyl pentanoic acid?CPADB?as the chain transfer agent?CTA?and 2,2?-Azobis?isobutyronitrile??AIBN?as the initiator,the thermo-sensitive copolymer poly?acrylic acid?-b-poly?N-isopropyl acrylamide??PAA-b-PNIPAM?was synthesized by sequentially polymerizing acrylic acid?AA?and N-isopropyl acrylamide?NIPAM?monomers via the reversible addition fragmentation chain transfer?RAFT?polymerization method.Then amidation modification of the copolymer was proceeded with ethylenediamine?EDA?to obtain poly[N-?2-aminoethyl?acrylamide)]-bpoly?N-isopropylacrylamide??PNAEAM-b-PNIPAM?.The target products were confirmed via nuclear magnetic resonance spectrum and infrared spectroscopy.2.After the PNAEAM-b-PNIPAM solution and CdTe nanocrystals?CdTe NCs?were mixed,nanosized photoluminescent colloidal nanocrystals clusters?CNCs?were prepared through the self-assembly.It was discussed the impact of the content of loaded CdTe NCs,the component and concentration of polymer on the change of fluorescence intensity of CNCs with temperature in the work.It was shown that:?1?keeping component and concentration of the polymer constant,CNCs have roughly the same volume phase transition temperature?VPT?except the ratio of CdTe NCs and NAEAM in the polymer in 1:1;?2?as polymer concentration and CdTe NCs : NAEAM ratio remain constant,the polymer component has little effect on the VPT of CNCs;?3?when polymer component and CdTe NCs : NAEAM ratio hold constant,CNCs self-assembled with different concentration of polymer have almost the same VPT;?4?the [HS-C10mim]+ ligands with smart noncovalent interactions on the as-prepared nanocrystals render the CNCs rapid and reversible thermo-response performances in the range of 32?-33?.3.Silver nanoparticles?Ag NPs?were prepared and endowed temperature sensitive characteristics using PAA-b-PNIPAM as the stabilizer and sodium borohydride?NaBH4?solution as the reducing agent.And the conditions to synthesize Ag NPs were optimized.The as-synthesized Ag NPs were served as the catalyst in the reduction reaction of p-nitrophenol?4-NP?,to be a temperature responsive catalyst switch.The influences of reaction temperature and additional polymer concentration on the catalytic performance of Ag NPs were also discussed.The results showed that,?1?with the increase of reaction temperature,the catalytic reaction rate of as-synthesized Ag NPs rises,then remains unchanged,finally drops;?2?as additional polymer is added to the system,catalytic reaction rate of Ag NPs firstly increases,then drops with raising temperature;the reaction stops above 35?;?3?the higher the content of polymer,the slower the catalytic reaction rate.The silver catalyst prepared in this work has high catalytic activity with a catalytic factor of 6950 s^-1·g^-1 and can be recycled and reused by the heating-centrifugation method.