| Larch bark is an important by-product of forestry in China.It is a renewable green resource with wide source and abundant quantity.The bark is rich in proanthocyanidins,which is a valuable natural product.It is inevitable that there will be interface incompatibility when it is prepared with polymer materials with different structures.This research is based on quantitative interpretation requirements and the characteristics of the proanthocyanidins/PVA polymer composite system,combined with the existing research progress in surface theory,interface theory,polymer materials,biomass materials and other related fields,this paper introduces the solubility parameter theory(Solubility Parameter)to start from the surface and interface research of proanthocyanidins and PVA polymer materials,infer the compatibility of polymer blends based on the theory of interface compatibility and select appropriate blending components,on the one hand,make the composite materials have the functionality of proanthocyanidins.Characteristics,on the other hand,deeply explore the influence of blending ratio on the compatibility and some properties of composite materials,and establish the relationship model between the solubility parameters of proanthocyanidins/PVA composite material and its mechanical properties and surface properties,and analyze correlation.The solubility parameters of proanthocyanidins before and after depolymerization and two commonly used PVA with different degrees of alcoholysis were calculated and verified by IGC method and molecular dynamics simulation method,and the surface properties and compatibility were evaluated by IGC method.According to the solubility parameter theory,PVA88 and LOPCs with similar solubility parameters were selected to prepare composite materials.And existing studies have shown that oligomeric proanthocyanidins(LOPCs)as a component of composite materials have better functionality than high-polymer proanthocyanidins(LPPCs).The main findings are as follows:The solubility parameters of LPPCs and LOPCs were determined by IGC at 298.15K.The solubility parameters of the two kinds of proanthocyanidins under the ideal model were obtained by molecular dynamics simulation.The results of IGC experiment were consistent with the results of computer simulation;At the same time,the specific retention volume Vg0 of proanthocyanidins on probe solvent at different temperature gradients was determined by IGC and the Flory Huggins interaction parameter ?12? and infinite dilution activity coefficient ?1?,and the changes of corresponding thermodynamic parameters between probe solvent and proanthocyanidin filler were investigated,and the results were analyzed regardless of the perspective that LOPCs were better soluble in phase with probe solvent than LPPCs;In addition,the surface energy component of the surface energy composition of procyanidin was calculated by the IGC method.The dispersive components ?sd of LPPCs and LOPCs decreased with the increase of temperature.The value of specific component ?ssp was smaller,which contributed less to the total surface energy ?s,and its distribution was scattered with temperature;The ?Gsp value was used to measure the deviation degree between the monopolar probe and the reference baseline of n-alkane series,so as to characterize the surface acidity and alkalinity of proanthocyanidins.The results showed that proanthocyanidins were amphoteric acid material.The comparison of ?Gsp value showed that LPPCs had strong acidity.When using PVA with two degrees of alcoholysis as the component of the composite material to study its surface and interface compatibility,the method and content of the study of two proanthocyanidins were the same.In addition,on this basis,the effect of the number of repeat units of PVA on the solubility parameters was supplemented,and the solubility parameters of PVA chains without repeat unit number were calculated at room temperature 298.15 K using molecular dynamics simulation,and the results of molecular dynamics simulation on the solubility parameters showed that:The changes in the solubility parameters of the PVA chain lengths with a repeat unit of 30 and above were not large,which indicates that PVA chains with a repeat unit of 30 and above can be selected on demand to calculate the solubility parameters.thus determining the appropriate PVA chain length;The results of the IGC experiment showed that the numerical trend of the solubility parameters of PVA88 and PVA99 at room temperature was the same as that of molecular dynamics simulation;the dispersive surface energy ?sd and specific surface energy ?ssp were scattered and hardly change with temperatured,and the dependence on temperature was small.And overall,the surface energy of PVA99 with a higher degree of alcoholysis was greater than that of PVA88 with a lower degree of alcoholysis;the value of ?Gsp showed that the two kinds of PVA studied are both amphoteric meta-acid materials,and PVA99 was more acidic.In the proanthocyanidins/PVA composite system,the solubility parameters of oligomeric proanthocyanidins LOPCs and PVA88 at room temperature were 22.09 and 22.68(J/cm-3)0.5,respectively,which were the most similar.According to the similarity compatibility theory,the composite system of LOPCs and PVA88 was selected;In addition,the LOPCs/PVA88 composite membranes with corresponding ratios were prepared to quantitatively study the mechanical and hydrophilic properties of blend membranes in relation to their solubility parameters.And the accuracy of the model was verified by statistical analysis as well as further computational simulation,which yielded a solubility parameter linear relationship with tensile strength as:Y=0.00719X2-0.5383X+27.24089(0<X<66.86),where X is the tensile strength and Y is the solubility parameter(?2)of the blends;solubility parameter vs hydrophilic contact angle:Y=0.5430X2-24.87X+313.79(15.96<X<24.17),where X is the solubility parameter of the complex(?2),Y is the hydrophilic contact angle of the composite membrane.The accuracy of the above relationship model was verified by statistical analysis and further simulation. |
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