Study On The Effect Of Side Group On The Physical And Chemical Properties Of Linear Polyphosphazene By Molecular Simulation

Glass transition is an important mechanical state transition phenomenon of polymer materials,and the corresponding glass transition temperature(Tg)is one of the important characteristic temperatures of polymer materials.Polyphosphazene is a kind of high polymer with alternating single and double bonds of phosphorus and nitrogen.The diversity and adjustability of side groups make it suitable for various application fields,the target Tg of polyphosphazene can be obtained by adjusting the type and content of side groups.In this paper,three series of polyphosphazenes’Tg with different proportion were simulated by molecular dynamics,and the thermal decomposition was analyzed.The polyphosphazene with cross-linking point was prepared to explore the application as fiber coating.Nine poly[(ethoxy)x/(phenoxy)yphosphazenes]were constructed.The Tg of polyphosphazenes was simulated by density method,specific volume method and non-bond energy method.The fox equation was obtained by experimental data.The simulation value,calculation value and experiment value all decreased with the increase of ethoxyl content,and the error of the three values was within 7℃.The ReaxFF force field of gulp module was used to simulate the thermal decomposition of all ethoxy/all phenoxy polyphosphazene.The small molecular substances and residues produced were in good agreement with the experimental values,which provided a theoretical basis for the experiment.Eight poly[(trifluoroethoxy)x/(phenoxy)yphosphazenes]were constructed.The Tg of polyphosphazenes was simulated by density method,specific volume method,non-bond energy method and free volume method.The error of simulation value of the four methods was within 3.5℃.Gulp and Dmol3 modules were used to simulate the thermal decomposition of perfluoroethoxy/octafluoropentoxypolyphosphazene,the small molecular substances and residues produced were in good agreement with the experimental values,which provided a theoretical basis for the experiment.The structure of the crosslinked fluoroalkoxy polyphosphazene was characterized by NMR,0.4 equivalent kh580 was used to modify polyphosphazene,5%polyphosphazene solution had the best effect on the modification of aramid fiber,and the tensile strength of aramid fiber increased by 17.7%and 16.7%respectively compared with the unmodified fiber under acid and alkaline conditions.Nine poly[(trifluoroethoxy)x/(phenoxy)yphosphazenes]were constructed.Five methods,density method,specific volume method,non-bond energy method,free volume method and radial distribution function method,were used to simulate the Tg of polyphosphazenes.The error of simulation value of the five methods was within 5.5℃,and the radial distribution function method was the highest.