Computer Simulation Study On Interfacial Properties In Homopolymer/Copolymer/Homopolymer Ternary Polymer Blends

Mixing two or more components with complementary properties is astraightforward and inexpensive way of creating new materials with improvedproperties. However, long polymers of different types are usualiy immiscible, becausethemixing free energy of is positive. Suitably chosen block or graft copolymers arewidely used in immiscible polymer blends as compatibilizers. This is due to theirinterfacial activity, i.e., to their affinity to selectively segregate to the interface betweenthe phase-separated homopolymers, which reduces the interfacial tension between thetwo macrophases, prevents coalescence, and enhances interfacial adhesion. Therefore, itis meaningful to investigate the interfacial properties of ternary polymer blendsincluding copolymers in guiding the development of polymer sciences and theproduction and application of polymer blend materials.The interfacial properties of homopolymer/copolymer/homopolymer ternarypolymer blends depend not only on the molecular weights and content of thecopolymers relative to those of the homopolymers, but also on the interaction parameterbetween the immiscible monomer, and on the macromolecular architecture/topologyand composition of the copolymers. In this thesis, we investigated the interfacialproperties of ternary polymer blends in micro-scale using Monte Carlo simulationmethod to reveal the intrinsic relevance between the interfacial properties and the chainlength and concentration of different copolymers. This research will be helpful forfurther understanding the interfacial properties, and will promote the development ofthe preparation, regulation and processing technology of polymer new materials.I. Monte Carlo Study on interfacial properties inhomopolymer/diblock copolymer/homopolymer ternary polymerblends When the volume fraction of diblock copolymer is fixed atC0.05, as thechain length of diblock copolymer increases from NC=10to NC=20, the interfacethickness decreases significantly. Whereas with the chain length of diblock copolymerfurther increasing to NC=60, the interface thickness increases slightly. The orientationparameter q of diblock copolymer chain enlarges with the increase of the diblockcopolymer chain length, which means that the diblock copolymer is more stretched;When the diblock copolymer chain length is fixed as NC=10and NC=40, as theconcentration of diblock copolymer increases, the interface thickness increases and thediblock copolymer chain orientation parameter q decreases, indicating that thestretching of diblock chain decreases.II. Monte Carlo Study on interfacial properties inhomopolymer/triblock copolymer/homopolymer ternarypolymer blendsWhen the volume fraction of triblock copolymer is fixed atC0.05, theorientation parameter q of triblock copolymer chain enlarges with the increase of thetriblock copolymer chain length. When NC>8, the orientation parameter q>0. Thisindicates that the triblock copolymer with longer chain length is more stretched andoriented in the z direction. As a result, each block penetrates deeper into its respectivehomopolymer phase when the chain length becomes longer. When the triblockcopolymer chain length are fixed as NC=20and NC=60, as the concentration oftriblock copolymer increases, the interface thickness increases and the chainorientation parameter q decreases first and then increases.III. Monte Carlo Study on interfacial properties inhomopolymer/multiblock copolymer/homopolymer ternarypolymer blendsWhen the volume fraction of multiblock copolymer is fixed atC0.05, as the chain length of multiblock copolymer increases from NC=12to NC=24, the interfacethickness decreases significantly, whereas with the chain length of multiblockcopolymer further increasing to NC=60, the interface thickness decreases. The chainorientation parameter q decreases with increasing multiblock copolymer chain length,and q<0, which means that the multiblock copolymer is not stretched in the z direction.When the multiblock copolymer chain length is fixed as NC=12, as the concentrationof multiblock copolymer increases, the interface thicknesstends to increase. Moreover,the chain orientation parameter q <0in all of the concentration, indicating that themultiblock copolymer is not stretched in the z direction.IV. Monte Carlo Study on interfacial properties inhomopolymer/graft copolymer/homopolymer ternary polymerblendsWhen the volume fraction of graft copolymer is fixed atC0.05, as themolecular weight of graft copolymer increases from NC=10to NC=60, theinterfacewith graft copolymer NC=20is the most thickness; The backbone orientationparameter of graft copolymer q<0, and the teeth orientation parameter q>0for allmoleculer weight. This indicates that the backbone is not oriented in the zdirection,and the teeth is oriented in the z direction. As a result, the backbone does not penetratedeeper into its respective homopolymer phase, the teeth penetrates deep into itsrespective homopolymer phase. When the graft copolymer chain length are fixed as NC=10and NC=60, as the concentration of graft copolymer increases, the interfacethickness increases, the backbone orientation parameter q is almost unchanged and theteeth orientation parameter tends to decreases.