Study On Effect Of Blending Amorphous Polymers On The Morphology And Structure Of Polycaprolactone Ultrathin Film

Polycaprolactone(PCL)can form melt compatible blends with polyvinyl chloride(PVC)and poly(4-vinylphenol)(PVPh).PCL/PVPh system has strong intermolecular hydrogen bonding interactions,while PCL/PVC system has weak intermolecular interactions.Two kinds of blending system ultrathin films were prepared by solution spin coating method,and the flower like,cauliflower like,“S” shaped,and anti “S” shaped worm like,as well as anti “S” shaped,truncated diamond shaped single crystals of PCL,were cultured by melt crystallization.The effects of crystallization temperature,blending mass ratio,ultrathin film thickness and molecular weight of amorphous polymer on the crystallization behavior of ultrathin films were investigated by optical microscope,atomic force microscope and transmission electron microscope.The main research results are as follows:1.In PCL/PVC blending ultrathin films,PCL is mainly grown as flower like/cauliflower like crystals.With the decrease of PCL content or film thickness,the crystals become worm like,with rubble like flakes growing obliquely toward the center of the flower like crystals.The orientation of lamellar in plane direction is poor.When the film thickness is reduced to about10 nm and the PVC content is 40%,the inverse “S” shaped single crystals of PCL can be cultured in the blending system,with a single layer lamellar thickness of about 5 nm.2.In PCL/PVPh blending ultrathin films,when the content of PCL is high and the crystallization temperature is low,the leaf like crystal unit fills the entire film,and the lamellae of the crystal unit presents a perfect flat-on orientation.PCL/PVPh(70/30)can form two types of truncated diamond shaped PCL single crystals with a film thickness of about 10 nm.The thickness of the single crystal layer is about 7 nm under low temperature crystallization and about 13 nm under high temperature crystallization.In situ recording of the growth process of PCL single crystals,the difference of single crystal morphology is due to the significant difference in growth rates between the a-axis and b-axis at low temperatures,while at high temperatures,the two gradually approach to each other.3.Comparing the two systems under the same thickness and crystallization conditions,it was found that the orientation of the lamellae in the PCL/PVC blending films was poor,and the growth of PCL was flower like.The flakes in PCL/PVPh blending films exhibit flat-on orientation,while PCL grows in a leaf like manner.It is speculated that this is due to the influence of intermolecular interactions on the orientation of flakes.The PCL/PVPh system exhibits strong intermolecular hydrogen bonding,while the PCL/PVC system exhibits weaker intermolecular interactions.