Study of the miscibility of poly(styrene-co-4-vinylbenzoic acid) with poly(ethyl methacrylate) or with poly[ethyl methacrylate-co-(2-N,N-dimethylaminoethyl) methacrylate] by inverse gas chromatography.
Poly(styrene) is immiscible with poly(ethyl methacrylate). The introduction of a small amount of 4-vinylbenzoic acid units along poly(styrene) chains (PS-VBA) enhanced its miscibility with poly(ethyl methacrylate) (PEMA) or with poly[ethyl methacrylate-co-(2-N,N-dimethylaminoethyl) methacrylate] (PEMA-DAE), as observed from the appearance of a single composition dependent glass transition temperature for each binary system using inverse gas chromatography. The negative values of the apparent polymer-polymer interaction parameter, chi(23)app, determined with different families of molecular probes, for three blend compositions and over a range of temperature confirm quantitatively the miscibility of these blends. The chi(23)app values for PEMA(PS-VBA) and (PEMA-DAE)-(PS-VBA) blends are dependent of the chemical nature of the probes, the temperature and the blend composition.
GC Investigation of the Solubility Parameters of Water-Soluble Homopolymers and Double-Hydrophilic Diblock Copolymers
Solubility parameters of water-soluble 2-(diethylamino)ethyl methacrylate (DEA) homopolymer and [2-(diethylamino)ethyl methacrylate]-[2-(dimethylamino) ethyl methacrylate] (DEA–DMA) diblock copolymer were analyzed by inverse gas chromatography and values were compared to the solubility parameters of 2-(dimethylamino) ethyl methacrylate (DMA) homopolymer. Sorption thermodynamic parameters of some aliphatic, alicyclic and aromatic hydrocarbons, weight fraction activity coefficients, Flory–Huggins interaction parameters and solubility parameters for both hydrocarbons and polymers were calculated. It was observed that sorption thermodynamic parameters on (co)polymers depend on the molecular structures of hydrocarbons. Evaluating both the calculated values of the weight fraction activity coefficients and Flory–Huggins interaction parameters, the solving ability of the hydrocarbons for DEA, DMA homopolymers and DEA–DMA diblock copolymer decreased in the following sequence: aromatic > alicyclic > aliphatic hydrocarbons.
Lower critical solution temperature behavior in polymer blends: compressibility and directional-specific interactions
Lower critical solution temperature (LCST) behavior in polymer blends is shown to be the result of the compressible nature of the system, the directional-specific character of the intermolecular interactions, or a combination of both. Certain random copolymer-homopolymer blends are examples of the first possibility. To illustrate the possibility of LCST behavior due to the directional-specific character of the intermolecular interactions, a recently introduced incompressible lattice-gas model by Vause and Walker is adapted to the polymer problem. Homopolymers are shown to be miscible if there is an acid-base interaction of sufficient strength and if the difference between the respective solubility parameters is not too large. The amount of entropy lost in the formation of a specific interaction is shown to be an additional important factor in determining polymer miscibility. Specific heat measurements can, in principle, decide whether the behavior of a polymer mixture at a given temperature is dominated by its compressibility or by the directional-specific interactions.