Synthesis And Properties Of Poly (Salicylic Acid) By Ring-Opening Polymerization

Salicylic acid(2-hydroxybenzoic acid)is a kind of naturally extractable phenolic acid,which plays an important role in modern medicine because of its heat clearing,anti-inflammatory and analgesic effects.Similar to other small molecule drugs,salicylic acid has a short half-life(about 2 hours)in vivo,which limits the use of salicylic acid as a drug in vivo.Because of its medicinal and metabolic characteristics,the polymer precursor drugs with many potential medical treatment can be produced by introducing the compound into the polymer,and the sustained release of salicylic acid can be realized by degradation or hydrolysis.At the same time,because of the change of crystallinity,degradation rate and biocompatibility of the copolymers,salicylic acid has been used in the modification of PLA,polyanine and PCL.The traditional process generally uses the method of melt condensation to synthesize poly(salicylic acid),but the method is low efficiency,high energy consumption and poor controllability.Therefore,it is very important to design a suitable reaction route to synthesize high molecular weight poly(salicylic acid)biomaterials.The main results of this work are as follows:Firstly,the synthesis method of salicylic acid-o-lactide(SA-OCA)monomer was explored with salicylic acid as raw material.Subsequently,a simple catalytic system composed of DBU and benzyl alcohol was used to catalyze the controlled ring opening polymerization of sa-oca monomer at room temperature.Through the screening of reaction conditions,when the ratio of catalyst DBU,initiator and monomer is 1/1/50,the reaction can be completed in 1 minute,and the reaction efficiency is very high.The molecular weight of polymer is Mn=5.68 KDa,and the molecular weight distribution is D=1.19.With the increase of monomer feed equivalent,the maximum molecular weight of polymer can reach Mn=14.10 KDa.Through the characterization and analysis of polymer by NMR and MS,the linear polymer with initiator terminated structure was obtained.In addition,the synthesized monomers are suitable for different initiators and Lewis base catalysts.Finally,the kinetics of polymerization was studied.