Study On Morphology Control And Mechanism Of Asymmetric Block Copolymer Compatibilization In Blend

This paper mainly explores regulation mechanism of binary phase morphology of asymmetric diblock copolymer polystyrene-b-poly(methyl methacrylate)(PS-b-PMMA)compatibilization poly(cyclohexyl methacrylate)/poly(methyl methacrylate)(PCHMA/PMMA)incompatible blend.Through this study,we lucubrate the process of mixing sequence,molecular weight of homopolymers,block ratio of asymmetric diblock copolymers,viscosity of the blend,micellar migration and diffusion behavior and relationship between kinetics and thermodynamics in process of asymmetric diblock copolymer compatibilizing,to find out the inherent law of these factors for the regulation of phase morphologies and mechanics performance of the blend with using theoretical calculation by the self-consistent field theory model(SCFT)and “Wet-Dry”brush theory to verify asymmetric block copolymer expansion for the essence of mechanism to control phase morphology of blend.The studies of this paper are as follows:1?In the second chapter of this paper,we use poly(cyclohexyl methacrylate)/poly(methyl methacrylate)(PCHMA/PMMA)incompatible blend as the research object to study competitive relations in process of mixing sequence of asymmetric diblock copolymer PS-b-PMMA compatibilizing PCHMA/PMMA blend: interface vs.micelles,so as to explore the phase morphologies change of incompatible blend by mixing sequence.Studies have shown that using best mixing sequence to add asymmetric diblock copolymer SM1(NPS/NPMMA=1:9)and SM2(NPS/NPMMA=9:1)and reduce homopolymer PMMA molecular weight in blend can significantly improve the phase morphology and domain size of dispersed phase,prompting asymmetric block copolymer at interface of two phases and improving the efficiency of compatibilization.It related to the dispersed phase viscosity and stability of thermodynamic state by micelles forming in blend.To increase PMMA molecular weight will change asymmetric block copolymer curvature of the interface between two phases,resulting in block copolymers are not stable at interface,and then spreading to PMMA phase to occur internal micelle,thus forming different micellar morphologies of dispersed phase.2?It has been clear about the mixing sequence affects phase morphologies of asymmetric diblock copolymer PS-b-PMMA compatibilizing PCHMA/PMMA blend.In the third chapter,we studies regulation mechanism and phase morphologies change of blend by block ratio of asymmetric diblock copolymer and molecular weight of homopolymer.The study found effect of that more symmetrical block ratio of asymmetrical diblock copolymer SM4(NPS/NPMMA=6:4)compatibilizing is much better,the domain size is much smaller,in the case of lower molecular weight of dispersed phase PMMA that block copolymer is basic at interface.Because of the effect of chain structure and ratio of asymmetric diblock copolymer SM1 and SM2 are easier to form micelles in bulk phase,SM3(NPS/NPMMA=8:2)fall in between SM1 and SM2.SCFT model calculation is also very good to explain this phenomenon.To regulate homopolymer molecular weight can change effect of external and internal emulsification,changing the swelling degree of segments can affect the utilization of block copolymer at the interface,but also affects the stability of asymmetric block copolymer at interface,it has also profound significance regulation of phase morphology of blend.More than that,the study also found that blend phase morphology with micelle are also reflecting the variation of blend performance at the same time.Asymmetry diblock copolymers compatibilizing,especially both 1:9 and 9:1 block ratio of SM1 and SM2 block copolymer not only failed to enhance tensile properties of the material,but as a result of reducing tensile strength of the blend for existence of micelle.3?To confirm the influence of asymmetric diblock copolymer PS-b-PMMA in PCHMA/PMMA that phase morphologies formed in blend by the micelle diffusion and thermodynamic stability of interface.In chapter fourth of this paper,we studies asymmetric diblock copolymer PS-b-PMMA micelle diffusion behavior and kinetics and thermodynamics of compatibilizing PCHMA/PMMA blend.The study found that micelle diffusion behavior affected by the viscosity of the blend,to increas viscosity of bulk phase to lead the slower of diffusion rate;and thermodynamic stability factor of micelle is also a vital factor to influence micelle diffusion,the longer of block segments,and phase which is compatible the blcok,the greater degree of "wet brush" is formed,chain interaction is much stronger at this time,the greater segments friction is also much stronger,the much difficulty of the segment of block movement,high molecular weight block copolymer in the bulk phase diffusion rate is slow,but the low molecular weight of block copolymer diffusion rate is fast in the bulk phase.Study also found that there were effects on the kinetics and thermodynamics of asymmetric diblock copolymer in incompatible blending,and also influenced by the ratio of asymmetric block and molecular weight of blend.Under the condition of low molecular weight of the dispersed phase,asymmetric diblock copolymer SM1,SM2 and SM3 compatibilizing PCHMA/PMMA incompatible blend,the dynamic barrier is much higher,thermodynamic is predominante,under the condition of relatively symmetric SM4 compatibilizing,dynamic barrier and thermodynamics barrier are not great,a predominance of thermodynamic factor is not obvious.Under the condition of high molecular weight of the dispersed phase,the SM1,SM2,SM3 and SM4 compatibilizing PCHMA/PMMA incompatible blend,thermodynamic barrier is much lower,thermodynamic is predominante as well,the effect of process of dynamic factors to asymmetric diblock copolymer compatibilizing PCHMA/PMMA incompatible blend is not very great.