Architectural Effects on the Solution Behavior of Linear and Star Polymers in Propane at High Pressures

Abstract

A star polymer with a divinylbenzene core and statistically random methacrylate copolymer arms is synthesized with reversible addition−fragmentation−transfer method and fractionated with supercritical carbon dioxide and propane to obtain fractions with low molecular weight polydispersity. The phase behavior and density behavior are experimentally determined in supercritical propane for fractionated star polymers and the corresponding linear copolymer arms at temperatures to 423 K and pressures to 210 MPa. Experimental data are presented on the impact of the number of arms, the backbone composition of the lauryl and methyl methacrylate repeat units in the copolymer arms, and the divinylbenzene core on the polymer−propane solution behavior. The star polymer is significantly more soluble because of its unique structure compared with the solubility of the linear copolymer arms in propane. The resultant phase behavior for the two homopolymers and the copolymer arms in propane are modeled using the perturbed chain statistical associating fluid theory (PC-SAFT). Model calculations are not presented for the phase behavior of the star polymers in propane because the PC-SAFT approach is not applicable for star polymer structures. ■ INTRODUCTIONOver the past few decades the advent of new chemistries has led to the creation of polymers with unique, well-defined architectures, such as star polymers with a fixed number of branches or, in other words, arms. Star polymers, with low to moderate molecular weight arms, have a globular structure that does not promote chain entanglements. Star polymers can be synthesized from a large range of homopolymer, block, and copolymer arms that can also contain functionilized groups. 1 Once the star polymer is synthesized the functional groups can be readily modified to adjust their physical properties for specific applications in the areas of catalysis, 1 coatings, 2 lubrication, 3 membrane formation, 4 and drug delivery. 5,6 Despite their increasingly mature applications, some fundamental physical properties, such as phase behavior and solution densities, are still lacking, and an accurate prediction of these properties over wide ranges of temperatures and pressures remains a challenge.Previously reported studies on star polymer−solvent solution behavior are typically performed with incompressible liquids at ambient pressure, not at high pressures with supercritical fluids. Star (sPS) and linear polystyrene (lPS) are primarily used in these studies to investigate the impact of multibranching architectural effects on solution behavior. Liquid solvents used for dissolving sPS and lPS include toluene, cyclohexane (CH), and methylcyclohexane (MCH), which, for these polymers, are characterized as a good, theta (Θ), and poor quality solvents, respectively. 7 Studies have been performed to determine the upper critical solution temperature (UCST), radius of gyration ⟨R g 2 ⟩, and second osmotic virial coefficient B 22 for sPS−solvent and lPS−solvent solutions at the same molecular weight M w , at d...

Fluid properties at high pressures and temperatures: Experimental and modelling challenges

“…Currently, many research laboratories use the synthetic technique with a variable-volume, view cell to visually observe and map the pressure, temperature, and composition of phase transitions. The versatility of the view cell apparatus is exemplified by its use for a wide range of applications, including the determination of vapor-liquid equilibria [17,18], the solubility of a polymer in pure and multicomponent solvents [19], the solubility of a solid in a supercritical fluid, the formation of gas hydrates, and the cloud point behavior of ionic liquid-CO2 systems.…”

Bubble and dew-point measurement of mixtures of 1H,1H,2H-perfluoro-1-octene and 1H,1H,2H,2H-perfluoro-1-octanol in supercritical CO2

“…Experimental investigations have been consistently published by Radosz et al, 15,16 Kiran et al, 17 Byun et al, 18,19 and McHugh et al. [20][21][22] Prior to the 1980s, a PB investigation for a binary model comprising a polymer in SCFs had been provided by Wolf and Blaum 23,24 and Cowie and McEwen. 25,26 A fluorine-containing olefin is a very economical intermediate, has a certain chemical activity, can derive a plurality of fluorine-containing organic materials, is a basic raw material for producing fluorine-containing fine chemicals and high polymer materials, and can be used for special purposes and for special purposes where it cannot be replaced by common organic materials in advanced industry and the like.…”

“…Experimental investigations have been consistently published by Radosz et al , 15,16 Kiran et al , 17 Byun et al , 18,19 and McHugh et al . 20–22 Prior to the 1980s, a PB investigation for a binary model comprising a polymer in SCFs had been provided by Wolf and Blaum 23,24 and Cowie and McEwen. 25,26…”

Hydrogen peroxide loaded cellulose acetate mats as controlled topical O2 delivery devices

“…H 2 O 2 release rate, O 2 production rate, and mat shelf-life data are also presented to demonstrate the efficacy of the in vitro performance of the H 2 O 2 -loaded CA mats. In the present study, H 2 O 2 -H 2 O solubility in CO 2 measurements are performed using a variable-volume view cell as described elsewhere [16,17]. The details of the variable-volume view cell are provided in the supporting information.…”