Preparation Of Multi-arms Star-Like Double Responsive Block Copolymer Via Photo ATRP

Star-like polymers are macromolecules consisting of multiple polymer chains of approximately equal lengths connected to a central core via one end.Star-like polymers attract considerable interest in macromolecular science due to their novel architectures and interesting properties in both solution and bulk phases and potential for high degrees of functionality relative to their linear counterparts.Star-like block copolymers have many unique properties because the star-like molecules combine special features of both block copolymers with tunable block composition and lengths,and star-like polymers,with compact structure,globular shape,and multifunctionality,into one entity.ATRP is a commonly used method for synthesizing star-like polymers.Compared with traditional ATRP,ppm copper photo ATRP has huge advantages,such as low cost,low metal content,certain oxygen resistance,and"green"Reaction etc.Stimulus-response polymer materials have attracted significant attention in various materials sectors.pH and thermosensitive star-like PAA-b-POEGA polymers with well-defined structure,controlled molecular weight and low polydispersity properties were prepared by photo ATRP.And Au and Ag nanoparticles were prepared using star PAA-b-POEGA as a nanoreactor.?1?The star-like PtBA is successfully prepared using a ppm-level copper-based photo ATRP system.First,we screened the reaction conditions of the experiment and obtained the optimal reaction ratio 600:1:0.01:0.04.And the kinetic study of star-like PtBA was carried out using this ratio.The critical conversion of star polymer was 45%.When the conversion is less than 45%,the reaction system has almost no termination?there is almost no diradical termination?.When the conversion rate is greater than 45%,the termination of the reaction system increases with intermolecular coupling terminates resulting in uncontrolled polymerization.?2?With the prepared star-like PtBA as a macroinitiator,a diblock star-like PtBA-b-POEGA was prepared by ppm-level copper-based photo ATRP,and TFA was used to selectively hydrolyze it to prepare double corresponding star-like PAA-b-POEGA.The synthetic star-like polymers were characterized by GPC,¹H NMR and FI-IR.The results showed that by adjusting the polymerization time,the single-arm molecular weights and ratio of PtBA block and POEGA block can be effectively controlled,and finally the molecular weight of each PAA arm can be controlled.?3?The properties of LCST and UCST was studied through UV/Vis and DLS.For the water system,when the temperature is lower than LCST,the star-like PAA-b-POEGA is dispersed,and it is transparent.When the temperature is higher than LCST,the star-like PAA-b-POEGA is aggregated,and a phase change occurs which is cloudy.In ethanol,when the temperature is lower than UCST,the star-like PAA-b-POEGA is aggregated,which is cloudy.When the temperature is higher than UCST,the star-like PAA-b-POEGA is dispersed,which is transparent.The LCST and UCST of star-like PAA-b-POEGA decrease with increasing POEGA segment ratio?block ratio P₂:P₁?,and LCST in water increases with pH increasing.The prepared star-like PAA-b-POEGA diblock polymer was used as a nanoreactor,HAu Cl₄·3H₂O and Ag NO₃ precursors were added to prepare Au and Ag nanoparticles.