Synthesis Of Thioctic Acid Ester Terminated Telechelic Polymers And Their Gelation In Base Oil

As cyclic disulfides have the properties of fast,reversible,and tunable disulfide exchange equilibria,with the capacity for responding to chemical,thermal and photochemical stimuli.We envisioned that ABA triblock copolymers where the terminal A blocks contain pendant 1,2-dithiolanes and the B block is a flexible oil-soluble PSMA would provide a class of structurally dynamic networks whose properties could be modulated by temperature or pH or by capping of the resultant free thiols.The dynamic polymersare widely applied for manufacturing of shock-absorbing cushioning materials,impact-resistant protective materials,self-healing materials,ductile materials,etc.However,such polymer dynamic materials are rarely applied in the field of tribology.In response to this problem,this master's degree thesis synthesized a series of telechelic polymers and studied their gel properties in base oils.The discussion will be conducted in the following three parts:In the first part,a series of ABA triblock copolymers TMAn-b-PSMA2m-b-TMAn(2m=10,20,40,80;n=2)have been synthesized,of which terminal A contains side chain 1,2-dithiolane,while the block B is oil-soluble PSMA,which forms dynamic covalent network structure and self-supporting oil gel by dissolving in PAO10 base oil.This type of dynamic sulfur-sulfur bond-based oil gel good viscoelasticity and higher yield stress,and it recovers faster after the structure is destroyed by high shear strength.Rheological test suggests that while keeping the length of block A still,with acceleration of block B,after enhance of strength of the gel,it tends to maintain still.According to SAXS and WAXS tests,though disordered structure,the WAXS test showed that signal peak corresponds to the octadecyl chain entanglement.It is thus concluded that this series of teleclaw polymers with lipoic acid end groups form oleogel in the base oil,and has good viscoelasticity,and the cyclic disulfide bond provides excellent lubrication performance.In the second part,different synthetic methods are used to study the the dynamic oil gel with a dynamic network structure formed in base oil of telechelic polymer TMAn-b-PSMA2m-b-TMAn(2m=24,70;n=8),which keeps the length of the block B remains still and changes the length of the block A.After preparation and characterization of the polymer,we found that polymers with longer block A lengths,and more sulfur-sulfur bond groups will be formed which further generate more dynamic cross-linking,and interlace to network structures.The structure will wrap the base oil and form gels.It can be seen from the observations that this type of dynamic sulfur-sulfur bond-based gel has better viscoelasticity and higher yield strength.and it has faster recovery efficiency after the structure is destroyed by high shear force.In the third part,ABA triblock copolymer Upyn-b-PSMA2m-b-Upyn(2m=24;n=4)containing pyrimidinone at the end group is synthesized,and studies on gel performance formed in the base oil.It is found that the block can form a quaternary hydrogen bond with self reaction in the base oil.By comparison,it is found that the insolubility of pyrimidone and its strong hydrogen bonding effect promotes formation of gel This type of quaternary-hydrogen-bond-based gel generates better viscoelasticity and higher yield strength,at the same time,it has faster recovery performance after the structure is destroyed by high shear force.