High pressure phase behavior for the binary mixture of pentafluoropropyl methacrylate and poly(pentafluoropropyl methacrylate) in supercritical carbon dioxide and dimethyl ether

Pressure-composition isotherm is obtained for the carbon dioxide+2,2,3,3,3-pentafluoropropyl methacrylate (PFPMA) using static apparatus with a variable volume view cell at temperature range from 40 °C to 120 °C and pressure up to 130 bar. This system exhibits type-I phase behavior with a continuous mixture-critical curve. The experimental result for carbon dioxide+PFPMA mixture was modeled using the Peng-Robinson (P-R) and multi-fluid nonrandom lattice fluid (MF-NLF) equation of state. Experimental cloud-point data of pressure up 470 bar and temperature to 182 °C were reported for the binary mixture of poly(2,2,3,3,3-pentafluoropropyl methacrylate) [Poly(PFPMA)] in supercritical carbon dioxide and dimethyl ether (DME). The Poly(PFPMA)+carbon dioxide and Poly(PFPMA)+DME systems showed LCST behavior.     

Monomer concentration effect on the phase behavior of poly(propyl acrylate) and poly(propyl methacrylate) with supercritical CO2 and C2H4

Experimental cloud-point data to temperature of 186 °C and pressure of ~2,500 bar are presented for ternary mixtures of poly(propyl acrylate)(PPA)-CO₂-propyl acrylate (PA) PPA-C₂H₄-PA and poly(propyl methacrylate) (PPMA)-CO₂-propyl methacrylate (PMA) systems. Cloud-point pressures of PPA-CO₂-PA system were measured in the temperature range of 32 °C to 175 dgC and to pressures as high as 2,070 bar with PA concentrations of 0.0, 5.0, 11.7 and 30.4 wt%. Adding 34.1 wt% PA to the PPA-CO₂ mixture significantly changes the phase behavior. This system changes the pressure-temperature slope of the phase behavior curves from U-LCST region to LCST region as the PA concentration increases. Cloud-point data to 170 °C and 1,400 bar are presented for PPA-C₂H₄-PA mixtures and with PA concentration of 0.0, 5.7, 15.5 and 22.2 wt%. The cloud-point curve of PPA-C₂H₄ system shows relatively flat at 730 bar for temperatures between 41 and 150 °C. With 15.5 and 22.2 wt% PA the cloud-point curve exhibits a positive slope that extends to 35 °C and ~180 bar. Also, the ternary PPMA-CO2-PMA system was measured below 186 °C and 2,484 bar, and with cosolvent of 5.2-20.1 wt%. PPMA does not dissolve in pure CO₂ to 233 °C and 2,500 bar. Also, when 41.5 wt% PMA is added to the PPMA-CO₂ solution, the cloud-point curve shows the typical appearance of a lower critical solution temperature (LCST) boundary.     

Photolysis of poly(benzyl methacrylate)s and poly(benzyl acrylate)s in solution and films

Methacrylate and acrylate copolymers containing benzyl or 1‐phenylethyl groups and their monomeric model compounds were irradiated with a 254‐nm light in CH₂Cl₂ and solid films. Low molecular weight and polymeric products were analyzed by gas chromatography (GC) and NMR spectroscopy, respectively, and main‐chain scission efficiencies were determined by gel permeation chromatography (GPC). The results indicate that the ester bond cleavage in the side chain produces alkyl radicals in the main chain, leading to main‐chain scission and crosslinking. The higher stability of tertiary alkyl radicals formed in methacrylate polymers lead to the predominant main‐chain scission in solution. On the other hand, acrylate polymers were less susceptible to photodegradation. The degradabilities of the polymer films reflected those of the polymer solutions, although crosslinking preferentially occurred. The distinct effect of oxygen on the degradation was also observed in solution and films. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2227–2236, 2001     

Phase behavior on the binary and ternary mixtures of poly(cyclohexyl acrylate) and poly(cyclohexyl methacrylate) in supercritical CO2

High‐pressure phase behavior was measured for the CO₂–cyclohexyl acrylate and CO₂–cyclohexyl methacrylate system at 40, 60, 80, 100, and 120°C and pressure up to 206 bar. This system exhibits type I phase behavior with a continuous mixture‐critical curve. The experimental results for the CO₂–cyclohexyl acrylate and CO₂–cyclohexyl methacrylate system were modeled using the Peng–Robinson equation of state. Experimental cloud‐point data, at a temperature of 250°C and pressure of 2800 bar, were presented for ternary mixtures of poly(cyclohexyl acrylate)–CO₂–cyclohexyl acrylate and poly(cyclohexyl methacrylate)–CO₂–cyclohexyl methacrylate systems. Cloud‐point pressures of poly(cyclohexyl acrylate)–CO₂–cyclohexyl acrylate system were measured in the temperature range of 40 to 180°C and at pressures as high as 2200 bar with cyclohexyl acrylate concentrations of 22.5, 27.4, 33.2, and 39.2 wt %. Results showed that adding 45.6 wt % cyclohexyl acrylate to the poly(cyclohexyl acrylate)–CO₂ mixture significantly changes the phase behavior. This system changed the pressure–temperature slope of the phase behavior curves from the upper critical solution temperature (UCST) region to the lower critical solution temperature (LCST) region with increasing cyclohexyl acrylate concentration. Poly(cyclohexyl acrylate) did not dissolve in pure CO₂ at a temperature of 250°C and pressure of 2800 bar. Also, the ternary poly(cyclohexyl methacrylate)–CO₂–cyclohexyl methacrylate system was measured below 187°C and 2230 bar, and with cosolvent of 27.4–46.7 wt %. Poly(cyclohexyl methacrylate) did not dissolve in pure CO₂ at 240°C and 2500 bar. Also, when 53.5 wt % cyclohexyl methacrylate was added to the poly(cyclohexyl methacrylate)–CO₂ solution, the cloud‐point curve showed the typical appearance of the LCST boundary. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1117–1125, 2004     

Phase equilibria of poly(methyl methacrylate) in supercritical mixtures of carbon dioxide and chlorodifluoromethane

Phase behavior data are presented for poly(methyl methacrylate) (PMMA: M_w= 15,000, 120,000) in supercritical solvent mixtures of carbon dioxide (CO₂) and chlorodifluoromethane (HCFC-22). Experimental cloud point curves, which were the phase boundaries between single and liquid-liquid phases, were measured by using a high-pressure equilibrium apparatus equipped with a variable-volume view cell at various CO₂ compositions up to about 63 wt% (on a polymer-free basis) and at temperatures up to about 100 °C. The cloud point curves exhibited the characteristics of a lower critical solution temperature phase behavior. As the CO₂ content in the solvent mixture increased, the cloud point pressure at a fixed temperature increased significantly. Addition of CO₂ to HCFC-22 caused a lowering of the dissolving power of the mixed solvent due to the decrease of the solvent polarity. The cloud point pressure increased with increasing the molecular weight of PMMA.     

Microcellular foaming of poly(phenylene sulfide)/poly(ether sulfones) blends using supercritical carbon dioxide

Microcellular foaming of poly(phenylene sulfide)/poly(ether sulfones) (PPS/PES) blends presents a promising approach to produce high‐performance cellular materials with tailored microstructures and enhanced properties. This study investigated the effects of multiphase blend composition and process conditions on the foaming behaviors and final cellular morphology, as well as the dynamic mechanical properties of the solid and microcellular foamed PPS/PES blends. The microcellular materials were prepared via a batch‐foam processing, using the environment‐friendly supercritical CO₂ (scCO₂) as a blowing agent. The saturation and desorption behaviors of CO₂ in PPS/PES blends for various blend ratios (10 : 0, 8 : 2, 6 : 4, 5 : 5, 4 : 6, 2 : 8, and 0 : 10) were also elaborately discussed. The experimental results indicated that the foaming behaviors of PPS/PES blends are closely related to the blend morphology, crystallinity, and the mass‐transfer rate of the CO₂ in each polymer phase. The mechanisms for the foaming behaviors of PPS/PES blends have been illustrated by establishing theoretical models. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42634.     

Structural aspects of the LCST phase behavior of poly(benzyl methacrylate) in room-temperature ionic liquid

The structure and lower critical solution temperature (LCST) phase behavior of well-defined poly(benzyl methacrylate) (PBnMA) solution using 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide, [C₂mim][NTf₂] ionic liquid (IL) as a solvent have been studied by dynamic light scattering (DLS) and small-angle neutron scattering (SANS) at various temperatures. The SANS profiles observed for fully deuterated IL ([C₂mim]-d₁₁[NTf₂]) containing PBnMA were kept practically unchanged in the temperature range between 298 and 363 K, while they suddenly changed at 363 K. This indicates that the LCST behavior of PBnMA-IL solution is a first-order phase transition, which is consistent with the DLS results. The SANS profiles below 363 K were well represented by the theoretical Debye scattering function with inter-molecular interaction and the radius of gyration, R_g was estimated to be almost constant, i.e., ∼45 Å. The SANS result obtained here was compared with those in aqueous PNIPAm solutions as a typical LCST system, and some differences between IL and aqueous solution systems are pointed out. It is found that thermodynamic quantities (ΔH_demix, ΔS_demix and ΔG_demix) from the homogeneous solution to the phase separation states strongly depend on the solvation of the PBnMA polymer by the IL ([C₂mim] cation and [NTf₂] anion). We propose an LCST phase separation mechanism in the polymer-IL solution.     

Cosolvent effect of water in supercritical carbon dioxide facilitating induced crystallization of polycarbonate

Water‐induced crystallization of polycarbonate (PC) was investigated in water‐saturated supercritical CO₂ (scCO₂) in the range of 80–160°C and 12–20 MPa, with the help of differential scanning calorimetry and wide‐angle X‐ray diffraction. Compared with pure scCO₂, the enhanced plasticizing effect of water‐saturated scCO₂ reduced the energy‐barrier for the motion of polymer chains, hence increased the crystallization rate of PC, and reduced the pressure threshold for crystallization from 14 to 12 MPa. On the other hand, the presence of water did not affect the thermodynamics of PC crystallization in scCO₂. A 3D‐diagram was established to show the relationship between crystallization and solubility parameter of mixed supercritical fluid at different temperatures and pressures. The results show clearly that the PC has a wider range of crystallization temperature and pressure in water‐saturated scCO₂ than in pure scCO₂, mostly because the addition of water increased significantly the solubility parameter of mixed supercritical fluid, and decreased the difference in solubility parameter between PC and water‐saturated scCO₂. POLYM. ENG. SCI., 47:1338–1343, 2007. © 2007 Society of Plastics Engineers     

Effects of supercritical carbon dioxide on crystallisation behaviour of polycarbonate/poly(methyl methacrylate) blends

SnCl₂·2H₂O-modified polycarbonate (PC)/poly(methyl methacrylate) (PMMA) (80/20?w/w) blends were prepared by melt blending using a torque rheometer. Supercritical carbon dioxide (scCO₂) has been used to induce the crystallisation of PC/PMMA blends while the crystallisation behaviour and morphology of these blend systems under different saturation temperatures, saturation pressures, saturation times and co-solvent contents were characterised by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The gravimetric experiment shows that the solubility of scCO₂ in PC/PMMA blends increases with the increase of saturation temperature, pressure and time. The DSC curves demonstrate that in these blend systems, the induced crystallisation of PC has been found and two kinds of crystals with different thicknesses exist in it. From the SEM images, it can be found that the structure of PC crystal becomes more perfect and its crystallinity also increases with the increase of saturation temperature, pressure, time and co-solvent content.     

High pressure phase behavior for the propionitrile and butyronitrile in supercritical carbon dioxide

Pressure-composition isotherms for the (carbon dioxide + propionitrile) and (carbon dioxide + butyronitrile) systems are measured in static-type high pressure apparatus at several temperatures of 313.2, 333.2, 353.2, 373.2 and 393.2 K and at pressures range from 3.5 to 16.7 MPa. The carbon dioxide + nitriles systems have continuous critical mixture (local) curves that exhibit maximums in pressure–temperature space between the critical point of carbon dioxide and monomers (propionitrile or butyronitrile). At a fixed pressure, the solubility of propionitrile or butyronitrile for the two binary systems increases as the temperature increases. The (carbon dioxide + propionitrile) and (carbon dioxide + butyronitrile) systems exhibit type-I phase behavior. The experimental results for the (carbon dioxide + propionitrile) and (carbon dioxide + butyronitrile) systems are correlated with Peng–Robinson equation of state using mixing rule including two adjustable parameters.     

超临界二氧化碳溶胀聚甲基丙烯酸甲酯的在线可视测量及热力学模拟计算

采用高压视窗釜配合高清晰相机研究了聚甲基丙烯酸甲酯(PMMA)在超临界二氧化碳(scCO₂)中溶胀行为,得到了PMMA在scCO₂中的平衡溶胀率。Sanchez-Lacombe(S-L)状态方程对于高压气体和聚合物系统的热力学性质有着很强的预测能力。将PMMA的PVT数据使用S-L状态方程进行拟合,得到压力、温度和密度的特征参数分别为：212.38 MPa、898.04 K以及1206.7 kg·m^-3 (8～25 MPa, 305～350 K),类似地可以得到二氧化碳(CO₂)的特征参数541.56 MPa、313.38 K以及1502.1 kg·m^-3 (8～25 MPa,305～325 K)。将实验得到的PMMA平衡溶胀率使用S-L状态方程拟合,可得二元相互作用参数为1.0671,结果表明在超临界区域,S-L状态方程模拟溶胀率与实验值吻合较好。     

High-pressure sorption of carbon dioxide in solvent-cast poly(methyl methacrylate) and poly(ethyl methacrylate) films

Carbon dioxide sorption isotherms in poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA) are reported for pressures up to 20 atm. Temperatures between 35 and 80°C were studied for PMMA and temperatures between 30 and 55°C were studied for PEMA. Typical dual mode sorption isotherms concave to the pressure axis were observed in all cases. The measured Langmuir sorption capacities of both polymers extrapolated to zero at the glass transition (T_g) consistent with the behavior of other glassy polymer/gas systems. Sorption enthalpies for CO₂ in the Henry's law mode for PMMA and PEMA are in the same range (?2 to ?4 kcal/mole) as has been reported for a variety of other glassy polymers such as poly(ethylene terephthalate), polycarbonate, and polyacrylonitrile. Some of the data suggest that postcasting treatment of the PEMA films left a small amount of residual solvent in the film. the presence of the trace residual solvent during quenching from the rubbery to the glassy state after annealing appears to cause a dilation of the Langmuir capacity and an alteration in the apparent Langmuir affinity constant of the PEMA film. These results suggest the possibility of tailoring physical properties of glassy polymers such as sorptivity, permeability, impact strength, and craze resistance by doping small amounts of selected residuals into polymers prior to quenching to the glassy state from the rubbery state.     

Dyeing poly(lactic acid) fibres in supercritical carbon dioxide

A study has been conducted into the dyeing of poly(lactic acid) fibres in supercritical carbon dioxide. The fibres were completely dyed using disperse dyes at 50 °C as shown by fibre cross-sections, although high colour depths in dark shades still prove challenging. Dye uptake increased significantly at temperatures ≥80 °C. At 95 °C in supercritical carbon dioxide, shrinkage and hardening of raw poly(lactic acid) were observed which could partly be overcome by the supercritical carbon dioxide extraction step. Afterclearing with cold supercritical carbon dioxide (to remove unfixed dye after dyeing) decreased the colour depth and led to non-uniform dyeing results on poly(lactic acid). Wash and rub fastness was good to very good also when poly(lactic acid) was not aftercleared in supercritical carbon dioxide. Fibre damage and elongation at break in supercritical carbon dioxide were similar to water.     

The reaction locus in supercritical carbon dioxide dispersion polymerization. The case of poly(methyl methacrylate)

The problem of determining the reaction locus in the supercritical carbon dioxide dispersion polymerization of methyl methacrylate is considered. For this, two limit models are comparatively evaluated using experimental data of polymerization kinetics and molecular weight distribution. The two models take opposite assumptions with respect to the relative rate of interphase radical transport with respect to the radical life time, which lead to different relative importance of the polymerization in the continuous or in the dispersed phase. The model parameters have been estimated using independent literature sources so as to ensure genuinely predictive modelling. The results clearly indicate that the interphase transport of the active chains is a key process in determining the reaction locus and it has to be carefully considered in order to reliably simulate any polymerization process of this type.     

A comparative study of poly(methyl methacrylate) and polystyrene/clay nanocomposites prepared in supercritical carbon dioxide

Poly(methyl methacrylate) and polystyrene/clay nanocomposites have been prepared via pseudo-dispersion polymerizations in the presence of a poly(dimethylsiloxane) surfactant-modified clay (PDMS-clay) in supercritical carbon dioxide. The effects of the PDMS-clay concentration on polymer conversion, molecular weight, and morphology have been investigated. The insoluble dispersion of PDMS-clay is shown to be an effective stabilizer for both MMA and styrene polymerization in scCO₂. The nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). While XRD shows featureless patterns for both nanocomposites, the actual distributions of clay are found to be quite different between PMMA and PS nanocomposites, presumably due to the different interaction mechanisms between the polymers and clay. Consequently, the different states of clay in the two nanocomposites play an important role in the mechanical properties of the nanocomposites, and a to a lesser degree in the thermal properties.     

Dynamic mechanical behavior of chlorosubstituted derivatives of poly(ethyl methacrylate) and poly(ethyl acrylate)

A freely oscillating torsional pendulum was used in the investigation of the influence of trichloroethyl, tetrachloroethyl, trichloromethoxyethyl, and trichloroethoxyethyl side groups on the molecular mobility in the glassy state and on the glass transition temperature of poly(meth)acrylates. All the polymers under study, which may be used as fire retardants, exhibit a simple relaxation behavior. While the parameters of the low-temperature and secondary relaxation process in the glassy state are not noticeably affected by the substituents used, the glass transition temperature T_g, increases with rising polarity and volume of side chains. The increase is larger in the series of polyacrylates, so that differences in the softening temperatures of polymethacrylates and polyacrylates having the same side chains decrease considerably with growing substitution.     

Synthesis and self-assembly of poly(benzyl ether)-b-poly(methyl methacrylate) dendritic-linear polymers

Here, the dendritic chloric poly(benzyl ether) (G₁-Cl, G₂-Cl and G₃-Cl) as the macroinitiator for the controlled atom transfer radical polymerization (ATRP) of methyl methylacrylate was investigated. Polymers obtained were characterizated by GPC, ¹H NMR, FT-IR, TGA and DSC. These dendritic-linear block polymers that consist of linear and dendritic segments have very good solubility in common organic solvents at room temperature. In a selective solvent (THF/H₂O), polymers can self-assembled into the micelles that have a spherical morphology in shape due to the lowest of the surface energies.     

Miscibility and phase behavior in blends containing random copolymers of poly(ether ether ketone) and phenolphthalein poly(ether ether ketone)

The miscibility and phase behavior of polysulfone (PSF) and poly(hydroxyether of bisphenol A) (phenoxy) with a series of copoly (ether ether ketone) (COPEEK), a random copolymer of poly(ether ether ketone) (PEEK), and phenolphthalein poly(ether ether ketone) (PEK-C) was studied using differential scanning calorimetry. A COPEEK copolymer containing 6 mol % ether ether ketone (EEK) repeat units is miscible with PSF, whereas copolymers containing 12mol % EEK and more are not. COPEEK copolymers containing 6 and 12 mol % EEK are completely miscible with phenoxy, but those containing 24 mol % EEK is partially miscible with phenoxy. Moreover, a copolymer containing 17 mol % EEK is partially miscible with phenoxy; the blends show two transitions in the midcomposition region and single transitions at either extreme. Two T_gs were observed for the 50/50 blend of phenoxy with the coplymer containing 17 mol % EEK, whereas a single composition-dependent T_g appeared for all the other compositions. An FTIR study revealed that there exist hydrogen-bonding interactions between phenoxy and the copolymers. The strengths of the hydrogen-bonding interactions in the blends of the COPEEK copolymers containing 6 and 12 mol % EEK are the same as that in the phenoxy/PEK-C blend. However, for the blends of copolymers containing 17, 24, and 28 mol % EEK, the hydrogen-bonding interactions become increasingly unfavorable and the self-association of the hydroxyl groups of phenoxy is preferable as the content of EEK units in the copolymer increases. The observed miscibility was interpreted qualitatively in terms of the mean-field approach. © 1996 John Wiley & Sons, Inc.     

Kinetics for free radical solution polymerization of heptadecafluorodecyl (meth)acrylate in supercritical carbon dioxide

Free radical solution polymerization of heptadecafluorodecyl acrylate (HDFDA) and heptadecafluorodecyl methacrylate (HDFDMA) was carried out by using 2,2′-azobisisobutyronitrile (AIBN) as the initiator in supercritical carbon dioxide (scCO₂). We performed solution polymerization with changing initiator concentration, temperature and polymerization time to study the polymerization kinetics. A nonlinear least square method and dead-end theory were used to determine the constant, K (K=(k _p √f)/√k _d k _d ) and initiator decomposition rate constant (k _d ) from experimental data. k _d was measured as 3.77 × 10⁻⁵ s⁻¹ at 62.7°C for poly(HDFDA) and 2.71 × 10⁻⁵ s⁻¹ at 62.5 °C for poly(HDFDMA), respectively, by nonlinear least square method.