The Effect And Application Of Janus Particles On The Compatibility Of Inherent Immiscible Blends Composed Of Silicone Rubber

The blending of polymers is a simple and effective way to improve the properties of materials and prepare shape memory polymers.Silicone rubber possesses many excellent properties based on its unique structure,such as wide operating temperature range,human comfort and biocompatibility etc,which has been widely used in harsh environment.Many specially properties can be given to silicone rubber by blending with thermoplastic polymers,such as heat and oil resistant property when blended with nylon,high strength,chemical stability and human comfort property when blended with thermoplastic polyurethane(TPU).It is difficult to obtain silicone rubber blending materials with excellent morphology,due to the great difference of chemical structure,polarity and the poor interface adhesion between apolar silicone rubber and polar plastics,and the aggregation of low surface tension silicone rubber.Therefore,it is crucial to improve the interface adhesion and compatibility of the immiscible phases by choosing appropriate compatibilizer for preparing silicone rubber/plastics blends with excellent morphology.However,the traditional compatibilizers,such as block and graft copolymers,are easy to form micelles and migrate from the interface into one phase and lose their compatibilizing ability during the process of blending.To solve this problem,different kinds of Janus particle compatibilizers were designed for silicone rubber/plastic blends,the relationships between the length,density and types of the grafted molecular chains and the dispersed phase size,the selectivity distribution of Janus particles and interfacial adhesion were investigated.Furthermore,high performance and high human comfort shape memory silicone rubber was prepared by applying the synthetic Janus particle compatibilizer.The main research contents of this subject are as follows:(1)For thermoplastic polyurethane/methyl vinyl silicone rubber(TPU/MVQ)blend,based on the snowman-like SiO2@PDVB Janus particle(JP),the PU-JP-PDMS hybrid Janus particle compatibilizer with polyurethane(PU)and polysiloxane(PDMS)molecular brushes was designed and synthesized.which were anchored at the interface,improved the interfacial adhesion and stability and decreased the dispersed phase size via the similar molecular chain entanglement at the interface and the sable amphiphilic conformation,compared with the unmodified JP particle and traditional polydimethylsiloxane-polybutadiene-polyurethanes(PU-PB-PDMS)triblock copolymer compatibilizer.Under the addition of only 1 wt%content addition through solution mixing,the size of the MVQ dispersed phase for TPU/MVQ/PU-JP-PDMS blends was reduced to 1/3,meanwhile,the strength and elongation of TPU/MVQ blend were also increased,compared with the TPU/MVQ without compatibilizer.(2)For nylon/methyl vinyl silicone rubber(PA/MVQ)blend,based on the snowman-like SiO2@PDVB Janus particle(JP),‘molecular brushes type'PA-JP-PDMS hybrid Janus particles and‘reactive type'Epoxy-JP-PDMS hybrid Janus particles compatibilizers were prepared,and Epoxy-JP-PDMS was easier to prepare and exhibited better dispersity than PA-JP-PDMS Janus particle.Then,the mechanism of Epoxy-JP-PDMS hybrid janus particles was explored,furthermore,the design idea of time-domain asymmetric compatibilizer was put forward.Under the guidance of the above mechanism,the reaction rate of reactive Epoxy-JP-PDMS particles with PA was slowed down by increasing the amount of PDMS grafting ratio,which avoided the agglomeration of Epoxy-JP-PDMS Janus particles and improved the dispersity of particles at the interface and compatibilization efficiency.When the grafting ratio of PDMS increased to 65 wt%,Under the addition of 3 wt%Epoxy-JP-PDMS,the dispersed phase size PA/MVQ/Epoxy-JP-PDMS-65%decreased from 100 ?m to 5 ?m compared with the PA/MVQ without compatibilizer.(3)For Methyl vinyl silicone rubber/polycaprolactone(MVQ/PCL)blend,based on the snowman-like SiO2@PDVB Janus particle(JP),the PCL-JP-PDMS hybrid Janus particle compatibilizer with polycaprolactone(PCL)and polysiloxane(PDMS)molecular brushes was prepared.The interfacial thickness and the elongation at break of MVQ/PCL blend could be increased effectively with increasing the grafting ratio of PDMS brush.When the grafting ratio of PDMS increased from 16.6 wt%to 66 wt%,the interfacial thickness of MVQ/PCL increased from 710 nm to 1240 nm.Meanwhile,the elongation at break of MVQ/PCL/PCL-JP-PDMS(66 wt%)blends increased by 259%,compared with the MVQ/PCL without compatibilizer.Subsequently,through using this stable molecular brush-type compatibilizer,comfort fitting shape memory silicone rubber with high fixity ratio(Rf=95%),high recovery ratio(Rr=99%),excellent mechanical properties,human comfort(E=5.9MPa)and impressive elasticity at room temperature was developed in this research.(4)In addition to preparing shape memory elastomers by blending with PCL as the reversible phase,the synthetic multi-functional shape memory elastomer(AN-TPU)was also prepared through PCL as the soft segment and anthracene-based diol as the chain extender.The cross-linked density of AN-TPU was tailored by UV irradiation time via the photodimerization of anthracene group,which improved the shape memory recovery ratio of AN-TPU.Even when the strain reached 270%,the shape recovery ratio and the fixity ratio were still both above 93%,which achieved the optimal value for shape memory performance.More importantly,the three-dimensional(3D)shape-free configuration was achieved through the dimerization of anthracene groups under UV irradiation,and through driven by temperature,the shape change spontaneously from two-dimensional(2D)to 3D was realized,which would have a wider range of potential application in stents.