Synthesis Of Functional Aliphatic Polyesters Via Step-Growth Polymerization Reaction

Aliphatic polyesters are a class of polymer materials with good biocompatibility and environmental degradability.They have been studied for nearly a century and are considered as potential substitutes for traditional non-degradable petroleum-based polymers.However,currently commercialized polyester materials still rely heavily on petrochemical resources,and their functional applications are relatively limited.In view of the above problems,this dissertation hopes to select monomers from biomass resources to avoid the dependence of synthetic polyester on petrochemical resources;use efficient stepwise polymerization to construct a series of aliphatic polyesters under mild and efficient conditions;During the synthesis process,the physical and chemical properties of polyester materials can be regulated and given new functions by introducing heteroatoms or functional groups.(1)Using the esterification reaction promoted by active ester,four kinds of long chain dicarboxylic acids/diols,eg.sebacic acid,decanediol,1,12-dodecanediol,and1,12-dodecanedioic acid are used.Monomer as raw material,in the catalytic system of N,N’-diisopropylcarbodiimide/4-dimethylaminopyridine p-toluenesulfonate(DIC/DPTS),the above diacid and four kinds of aliphatic polyesters P1-P4 with different carbon chain lengths and higher molecular weights were prepared by pairwise condensation polymerization between diols.Subsequently,a series of polythioether esters P5-P8 were synthesized under the catalysis of dimethylphenylphosphine(DMPP)by thiol-Michael polyaddition reaction using dithiol and bisacrylate as substrates.These polythioether esters are similar in structure to P1-P4 and correspond to each other.Only one methylene group is replaced by a sulfur atom in the polymer chain structure,and the polymer chain structure is changed with a small amount,giving the polymer good fluorescence performance and heavy metal adsorption ability,on this basis the effect of thioether bond on the physical and chemical properties of polyester was studied.(2)A castor oil-based bio-based plastic was synthesized,and its characterization and functionalization were studied.First,a high molecular weight aliphatic polyester P1 was obtained by self-polycondensation using the monomer 11-bromundecanoi acid,demonstrating the high efficiency of this stepwise polymerization method,which relies on efficient nucleophilic substitution between carboxylic acid anion and carbon-halogen moiety under alkaline condition.Subsequently,a series of copolymers P2-P5 with different compositions were prepared by random copolymerization of11-bromundecanoic acid and 6-bromohexanoic acid with different feed ratios.There is a linear positive correlation between the crystallization(T_c)and melting(T_m)temperatures of polymers P1-P5 and the molar fraction of 11-bromundecanoic acid in these random copolymers.Differential scanning calorimetry(DSC)and wide-angle X-ray diffraction(WAXD)results indicate that these bioplastics have good crystallinity.Furthermore,the degradation of polymers P1-P5 was facilitated by the external alkaline environment while hindered by their inherent hydrophobicity,suggesting that p H and composition are two important factors controlling the degradation behavior of biobased polyesters in the bulk state.Finally,the polymerization of 11-bromundecanoic acid was carried out in the presence of1-pyrenebutyric acid,an end-capping agent,to obtain a functionalized polymer P7containing pyrene at the chain end groups.The material can be used as a practical fluorescent probe and dispersion stabilizer for multi-walled carbon nanotubes(MWNTs).