Accounting for Cooperativity in the Thermotropic Volume Phase Transition of Smart Microgels

A full quantitative description of the swelling of smart microgels is still problematic in many cases. The original approach of Flory and Huggins for the monomer–solvent interaction parameter χ cannot be applied to some microgels. The reason for this obviously is that the cross-linking enhances the cooperativity of the volume phase transitions, since all meshes of the network are mechanically coupled. This was ignored in previous approaches, arguing with distinct transition temperatures for different meshes to describe the continuous character of the transition of microgels. Here, we adjust the swelling curves of a series of smart microgels using the Flory–Rehner description, where the polymer–solvent interaction parameter χ is modeled by a Hill-like equation for a cooperative thermotropic transition. This leads to a very good description of all measured microgel swelling curves and yields the physically meaningful Hill parameter ν. A linear decrease of ν is found with increasing concentration of the cross-linker N,N′-methylenebisacrylamide in the microgel particles p(NIPAM), p(NNPAM), and p(NIPMAM). The linearity suggests that the Hill parameter ν corresponds to the number of water molecules per network chain that cooperatively leave the chain at the volume phase transition. Driven by entropy, ν water molecules of the solvate become cooperatively “free” and leave the polymer network.

A Molecular Dynamics Study on the Miscibility and Morphology of Polyester Blends used in Coil Coatings

Computational simulations can be used to save on both time and costs, complementing experimental work and providing further guidance. Immiscible polymer blends induce phase segregation, and in some cases can produce useful multicoat systems. This works uses a range of Molecular Dynamics Simulations methods, including an extended Flory Huggins Interaction Parameter χ to initially probe the interactions and miscibility between ester monomers commonly used in coil coatings. This work indicates that blends with similar backbone structures or “like with like” show increased miscibility and those with different structures lead to a large χ value and immiscibility. Further to this, polyester blends with different backbone structures have then been coarse grained with MARTINI beads and simulations of 10 µs have been run to identify the morphology of the blends at the mesoscopic level. Finally, the melamine crosslinker commonly used in polyester formulations has previously been shown to form agglomerates at higher melamine content, these agglomerates have been shown in atomistic simulations.

A Molecular Dynamics Study on the Miscibility and Morphology of Polyester Blends used in Coil Coatings

Computational simulations can be used to save on both time and costs, complementing experimental work and providing further guidance. Immiscible polymer blends induce phase segregation, and in some cases can produce useful multicoat systems. This works uses a range of Molecular Dynamics Simulations methods, including an extended Flory Huggins Interaction Parameter χ to initially probe the interactions and miscibility between ester monomers commonly used in coil coatings. This work indicates that blends with similar backbone structures or “like with like” show increased miscibility and those with different structures lead to a large χ value and immiscibility. Further to this, polyester blends with different backbone structures have then been coarse grained with MARTINI beads and simulations of 10 µs have been run to identify the morphology of the blends at the mesoscopic level. Finally, the melamine crosslinker commonly used in polyester formulations has previously been shown to form agglomerates at higher melamine content, these agglomerates have been shown in atomistic simulations.

A Molecular Dynamics Study on the Miscibility and Morphology of Polyester Blends used in Coil CoatingsA Molecular Dynamics Study on the Miscibility and Morphology of Polyester Blends used in Coil Coatings

Computational simulations can be used to save on both time and costs, complementing experimental work and providing further guidance. Immiscible polymer blends induce phase segregation, and in some cases can produce useful multicoat systems. This works uses a range of Molecular Dynamics Simulations methods, including an extended Flory Huggins Interaction Parameter χ to initially probe the interactions and miscibility between ester monomers commonly used in coil coatings. This work indicates that blends with similar backbone structures or “like with like” show increased miscibility and those with different structures lead to a large χ value and immiscibility. Further to this, polyester blends with different backbone structures have then been coarse grained with MARTINI beads and simulations of 10 µs have been run to identify the morphology of the blends at the mesoscopic level. Finally, the melamine crosslinker commonly used in polyester formulations has previously been shown to form agglomerates at higher melamine content, these agglomerates have been shown in atomistic simulations.

MD simulation studies of the physical and mechanical properites of P3HT-based blends

In this research, the physical and mechanical properties of semi-crystalline polymerpoly-(3-hexylthiophene-2,5-diyl)-based blends were investigated. The volume versus temperature curves of polymerpoly-(3-hexylthiophene-2,5-diyl)/methano-fullerene derivative[6]-phenyl-C64-butyricacidmethyl ester (P3HT:PCBM) and polymerpoly-(3-hexylthiophene-2,5-diyl)/DOCN-PPV (P3HT/CNPh-PPV) were plotted; however, we obtained one single temperature for each curve between glass transition temperatures of the compounds, which could be considered a good indicator of miscibility. In addition, the Coesif energy density of P3HT, PCBM, and CNPh-PPV were calculated and used to obtain the solubility parameters δP3HT, δPCBM, and δCNPh-PPV. The interaction parameter χ was calculated and used in the investigation and we confirmed the miscibility of our polymer systems. By using the dissipative particle dynamic method, the morphologies of P3HT/PCBM and P3HT/CNPh-PPV were enhanced.

Phase Diagrams of n-Type Low Bandgap Naphthalenediimide-Bithiophene Copolymer Solutions and Blends

Phase diagrams of n-type low bandgap poly{(N,N’-bis(2-octyldodecyl)naphthalene -1,4,5,8-bis(dicarboximide)-2,6-diyl)-alt-5,5′,-(2,2′-bithiophene)} (P(NDI2OD-T2)) solutions and blends were constructed. To this end, we employed the Flory–Huggins (FH) lattice theory for qualitatively understanding the phase behavior of P(NDI2OD-T2) solutions as a function of solvent, chlorobenzene, chloroform, and p-xylene. Herein, the polymer–solvent interaction parameter (χ) was obtained from a water contact angle measurement, leading to the solubility parameter. The phase behavior of these P(NDI2OD-T2) solutions showed both liquid–liquid (L–L) and liquid–solid (L–S) phase transitions. However, depending on the solvent, the relative position of the liquid–liquid phase equilibria (LLE) and solid–liquid phase equilibria (SLE) (i.e., two-phase co-existence curves) could be changed drastically, i.e., LLE > SLE, LLE ≈ SLE, and SLE > LLE. Finally, we studied the phase behavior of the polymer–polymer mixture composed of P(NDI2OD-T2) and regioregular poly(3-hexylthiophene-2,5-dyil) (r-reg P3HT), in which the melting transition curve was compared with the theory of melting point depression combined with the FH model. The FH theory describes excellently the melting temperature of the r-reg P3HT/P(NDI2OD-T2) mixture when the entropic contribution to the polymer–polymer interaction parameter (χ = 116.8 K/T −0.185, dimensionless) was properly accounted for, indicating an increase of entropy by forming a new contact between two different polymer segments. Understanding the phase behavior of the polymer solutions and blends affecting morphologies plays an integral role towards developing polymer optoelectronic devices.

Transparency, ultraviolet transmittance, and miscibility of poly(lactic acid)/poly(methyl methacrylate) blends

Poly(lactic acid)/poly(methyl methacrylate) (PLA/PMMA) blends were prepared by melt compounding technique. The miscibility of PLA/PMMA blends at various blending ratios (i.e. 80/20, 60/40, 40/60, and 20/80) was investigated using a dynamic mechanical analyzer (DMA) and solvent uptake experiment. The solvent uptake experiment was conducted to estimate the interaction of PLA/PMMA blends based on the calculation of Flory–Huggins interaction parameter ( χ12). DMA results revealed that only single glass transition temperature ( Tg) existed along the PLA/PMMA blends. Smallest χ12 (i.e. −0.03) was found on the PLA/PMMA20 blend, suggesting interaction between PLA and PMMA at this composition. The incorporation of PMMA slightly improved the UV protection properties of the PLA/PMMA blend, while maintaining their optical transparency.