Synthesis Of Novel Catechol-functionalized Alternating Copolymers And The Study On Adhesive Properties

Marine mussels have the ability to cling to various surfaces at wet and turbulent environment by secreting catechol-containing mussel foot proteins,which inspires the research of incorporating catechol groups into designed polymer to develop mussel-inspired high-performance adhesive materials.However,there exists at least two problems in this process.Firstly,the preparation steps of catechol-functionalized polymers are tedious.Polymerizable groups like double bonds should be incorporated into catechol structures first before polymerization.Secondly,it is still high challenging to prepare catechol-functionalized polymers with excellent adhesive performance both at dry and underwater conditions.Most of catechol-functionalized polymers could bond substrates only at atmospheric environment,and limited catechol-functionalized polymers could bond substrates at wet or underwater situation.However,the catechol-functionalized polymers applicable to the high-performance adhesion at both dry and underwater state are quite rare.To address these challenges,two different catechol-functionalized alternating copolymers were synthesized and the bonding performance at both dry and under-seawater conditions were studied in this dissertation.The detailed contents were described as follows:（1）A novel catechol-functionalized alternating copolymer P（DA-a-BGOP）was synthesized from the copolymerization between dopamine and 2,2-bis（4-glycidyloxyphenyl）propane monomers via an epoxy-amino click reaction.The obtained P（DA-a-BGOP）alterenating copolymer was used as an adhesive material.The results showed that after curing at 200℃ and 10 MPa for 20 min,P（DA-a-BGOP）could achieve excellent bonding strength on various substrates,among which the highest bonding strength was 16.39±2.13 MPa on stainless steel substrates.By comparing with other alternating copolymers,we believed that the strong adhesive properties of P（DA-a-BGOP）were caused by the good balance between cohesive and adhesive bonding interactions,which were induced by catechol moieties and bisphenol A structures in the alternating copolymers.Then,the effects of cross-linking agents’type,cross-linking agents’dosage,the polymer solution concentration and the substrates’s type on the under-seawater bonding strength were investigated.The results showed that when FeCl₃ was used as cross-linker,the mole ratio of Fe³⁺to catechol was 1:3 and the polymer solution concentration was 0.45 g/m L,P（DA-a-BGOP）could achieve excellent under-seawater bonding strength on various substrates.For example,the highest bonding strength obtained on glass substrates was 1.05±0.05 MPa,which is one of the best performance on glass substrates.Also,bonding strength of this novel alternating copolymer was benchmarked against several commercial systems,demonstrating that P（DA-a-BGOP）can be used as a high-performance adhesive material both at dry and underwater conditions.（2）A novel catechol-functionalized alternating copolymer P（DA-a-BAER）,containing more than one bisphenol A structures in the constitutional unit,was synthesized from the copolymerization between dopamine and bisphenol A epoxy resin monomers via an epoxy-amino click reaction.The resultant alternating copolymer was used as an adhesive material,of which the bonding performance was investigated with the usage of FeCl₃ as cross-linker.The results showed that P（DA-a-BAER）could bond various substrates both at dry and underwater conditions,among which the highest bonding strength was achieved on stainless steel substrates:at atmospheric situation,when the mole ratio of Fe³⁺and catechol groups was 1:3,the highest bonding strength was 3.03±0.68MPa;at under-seawater condition,when the mole ratio of Fe³⁺and catechol groups reached 1:6,the highest bonding strength was 0.65±0.10MPa.The crosslinking mechanism of Fe³⁺was studied by Raman spectrum and UV-Visible（UV-Vis）absorption spectrum,demonstrating that catechol moieties underwent oxidation crosslinking and coordination crosslinking processes.As a result,the cohesion strength of the polymer was enhanced,leading to a high bonding strength.