Synthesis Of Pressure Sensitive Adhesives From Triblock Copolymer And Analysis Of Their Adhesive Behavior

Pressure-sensitive adhesives from block copolymers show the adhesive superiority in the structural design and controllability,which are widely used in the fields of wearable device and electronic device package.Commonly such pressure-sensitive adhesives often contain another additives and block polymers matrix which consists of a soft segment with a low glass transition temperature(T_g)and a hard segment with a high T_g,which makes the system much more complicate in preparation and structural analysis.Therefore,a simple strategy to pressure-sensitive adhesive from block copolymer with a clear structure and excellent adhesion performance is an important subject in the field of soft matter research,and shows the important theoretical practical value.In this work,we designed a novel pressure-sensitive adhesive based on an amphiphilic triblock copolymer via atom transfer radical polymerization(ATRP)that consists of the hydrophobic end blocks of poly(benzyl acrylate)(PBz A)with high T_g and hydrophilic mid-block of poly(2-hydroxyethyl acrylate)(PHEA)with low T_g.A polymer pressure-sensitive adhesive with a three-dimensional network structure was formed due to the occurrence of microphase segregation induced by immiscibility of such block segments under thermal dynamic equilibrium.The obtained pressure-sensitive adhesive shows the excellent and recoverable adhesion properties,and on-demand detachment properties.The main research contents are as follows:(1)An amphiphilic triblock polymer pressure-sensitive adhesive PBz A-b-PHEA-b-PBz A was prepared by ATRP polymerization method and silyl ether group deprotection method.By adjusting the feed ratio and reaction time,three pressure-sensitive adhesives with different components were successfully synthesized.These adhesives have the glass transition temperature much lower than room temperature,and their modulus is in the range of 10-100k Pa,which is in line with Dahlquist rules of adhesive materials.(2)Multiple structural characterization methods revealed that microphase separation occurs in the bulk materials,and the hydrophobic segment aggregation serves as the"chemical crosslinking point"of the system,imparting the integrity of the material,and also provide the adhesion abilities with various interfaces.The hydrophilic segment aggregation formed by the association of hydrogen bonds can be broken upon loading and reformed after unloading,dissipating viscoelastic energy to enhance the mechanical strength and adhesive properties.(3)The effect of contact force,contact time,test temperature and peeling rate on the maximum stress and adhesion energy of the pressure-sensitive adhesive were systematically explored via a probe test method.The results showed that the time-temperature superposition principle is basically obeyed not only for the small strain rheology but also for the large strain maximum stress(yield stress)and adhesion energy in a range of probed temperature.It indicated that the adhesion properties are mainly from the viscoelastic energy dissipation of the bulk material.Furthermore,the pressure-sensitive adhesives show the reversible adhesion and on-demand detachment,which plays a key role in the engineering area.In this thesis,a bottom-up design strategy to pressure-sensitive adhesives from block polymers were performed,which provides a way to understand their relationship between"composition-structure-performance".This work gives an insight into designing novel pressure-sensitive adhesives and laying a good foundation for the practical application.