Loading Repair Agent And PH-responsive Of Cross-linked Micelle Self-assembled By Triblock Copolymers

In this paper,the pH-responsive triblock copolymer PEG-PDMAEMA-PBMA with a certain molecular weight was synthesized by ATRP.The assembles before and after cross-linked at different pH values were prepared by dialysis method.The results showed that the assembles could respond to the change of pH.When the pH value was reduced from 9.7 to 7.4,the morphology and structure of the assembly were destroyed,and the assembly tended to change from microspheres(uncrossliced)or adhesives(after crosslinking)to small micelle.When the pH decreases to 3.0,the assembly disperses to form a small micelle.The assembly can load with coating repair agent DCPD,and the carrier is unstable,which is easy to cause the leakage of DCPD.After cross-linked,the carrier adheres and overlaps,and there is no leakage of the agent.The carrier has the behavior of releasing DCPD in response to pH.Under near-neutral conditions pH=7.4,DCPD is released in a small amount,while under acidic conditions pH=3.0,DCPD is almost completely released.Cross-linked can improve the stability of the carrier,reduce the release of DCPD under the same conditions,and still has the ability to encapsulate part of DCPD under acidic conditions.The experiment was validated and extended to a certain extent by the simulation method of dissipative particle dynamics(DPD).The results show that the hydrophilic block is longer and the hydrophobic block is shorter in the spheroidizing concentration range,and the assembly tends to form a vesicle structure with a middle depression.The shorter hydrophilic block can not encapsulate the repair agent DCPD,only when the hydrophilic and hydrophobic blocks are in a moderate proportion.The filling process of DCPD is the migration process of DCPD from the surface of micelle to the inside.The structure of micelle is changed from double-layer core(other hydrophobic beads)-shell(EG)structure to three-layer core(DCPD)-intermediate layer(other hydrophobic beads)-shell(EG),the volume of microspheres is unchanged,the density is increased,and the stability of the carrier is poor.Cross-linked can improve the stability of the carrier.When the pH-response blocks are protonated to varying degrees,the carrier can not be dispersed due to the existence of cross-linked,which still has a certain encapsulation effect on DCPD.Compared with the non cross-linked carrier,crosslinked may lead to slow and incomplete release of DCPD,which is conducive to effective encapsulation and controlled release of restorants in micelles.