Computer Simulation Of Block Copolymer Blending System Based On PLA

Polylactic acid（PLA）is a thermoplastic,which has the advantage of being biodegradable into harmless substances and has biocompatibility.It is widely used in various fields such as biomedicine and packaging materials.One of the most effective ways to toughen and modify polylactic acid is to introduce other fragments with better toughness into the main chain structure by means of block copolymerization.Polyethylene glycol（PEG）is a kind of biocompatible,non-toxic.A polymer that can be used for block copolymerization with PLA.In this experiment,a PLA-b-PEG-b-PLA triblock copolymer was designed based on polylactic acid,and blended with different modifiers as an alternative for preparing polylactic acid composites.Finding suitable block fractions of PLA and PEG and a modifier with good blend compatibility are the keys to improving the properties of the prepared composites.Computer simulation is conducive to finding the best formula,which can effectively save development time and cost and improve development efficiency.Based on this,this study used computer simulation to explore the blend system of PLA-b-PEG-b-PLA triblock copolymer based on polylactic acid and different modifiers to obtain an optimized formulation with the best performance.The main research contents are as follows:（1）In order to preliminarily screen out two blending components with relatively good blend compatibility,the Visualizer module in the MS8.0 calculation software was used to establish polylactic acid and polyethylene with block fractions of 0.1,0.3,and 0.5,respectively.Three triblock copolymers of diols[PLA₃-PEG₅₀-PLA₃（BL1）,PLA₁₁-PEG₅₀-PLA₁₁（BL2）,PLA₂₅-PEG₅₀-PLA₂₅（BL3）]and six modifiers,namely starch（Amylose）,The molecular chain model of polyethylene glycol（PEG）,polyvinyl chloride（PVC）,dioctyl phthalate（DOP）,nylon-11（PA11）,tributyl citrate（ATBC）corresponding to the degree of polymerization,and then The Blends module was used to simulate the blending between the block polymer and the modifier components,respectively,and the blend compatibility was compared by comparing the binding energy,mixing energy,and interaction parameters of different combinations.Among the various blending combinations,the binding energy curves of BL3 and Amylose are the most similar,and the mixing energy is significantly lower than that of other blending components when the mixing energy is below 353K,indicating that their blending compatibility is good.（2）The selected BL3/Amylose combination was further simulated for compatibility with different blending mass ratios by molecular dynamics simulation method,and the mass ratios were set as 10/90,30/70,50/50,70/30,90/10,and the mechanical properties of the blended components of each mass ratio were simulated by the constant strain method.When the mass ratio is 50/50,the interaction parameters of the blend system are less than the critical value,and the results of the mechanical properties simulation show that the compressive modulus,bulk modulus,shear modulus and Young’s modulus are in the mass ratio of 50/50.At this time,the value is smaller than that of other mass ratio components,which verifies that the toughness of the blend at this time is better than that of the blend components of other mass ratios.At this time,the toughening effect of the modifier is the best,indicating that the molecular dynamics simulation method is used.The resulting optimal blend ratio was 50/50.（3）The glass transition temperature of the pure substance and blend components of BL3/Amylose were simulated and predicted,and the volume,density,and force field energy terms（including bond energy,bond energy,The relationship between angular energy,torsional energy,non-bonding energy）and temperature was analyzed and discussed.The most important characteristic temperature of polymer materials can be obtained by simulating and predicting the glass transition temperature of the blended components,which helps to analyze the movement of the molecular chains of the blended polymer at the macroscopic level.