Design of CO2 Thickeners and Role of Aromatic Rings in Enhanced Oil Recovery Using Molecular Dynamics

Oligomers of PDMS (M1), polyFast (M2), modified PVEE (M3 and M4), and two new molecules with cyclic cores (M5 and M6) were studied to understand their ability to thicken the sc-CO2 at 377 K and 55 MPa, without any cosolvent. It was observed that PDMS and polyFast behaved in the known ways. PDMS does not improve the viscosity of the system without a cosolvent and PolyFast enhances the viscosity by a large margin. M3 and M4 also have not improved the viscosity significantly even with the introduction of a styrene component, but which has improved their solubilities in the fluid. M5 and M6, however, are observed to have enhanced the viscosity similar to that of polyFast due to their structural advantage and π-π interactions between the molecules. These molecules were also tested for their synthesizability, and their synthesis is found to be moderately easy.

Antimicrobial ‘inks’ for 3D printing: block copolymer-silver nanoparticle composites synthesised using supercritical CO2

A new synthetic methodology to produce polymer-AgNP composite microparticles using scCO2 is presented. These microparticle possessed long-lived antimicrobial activity and were tested for compatibility in the Laser Sintering 3D printing process.

Data Mining of Polymer Phase Transitions upon Temperature Changes by Small and Wide-Angle X-ray Scattering Combined with Raman Spectroscopy

The complex physical transformations of polymers upon external thermodynamic changes are related to the molecular length of the polymer and its associated multifaceted energetic balance. The understanding of subtle transitions or multistep phase transformation requires real-time phenomenological studies using a multi-technique approach that covers several length-scales and chemical states. A combination of X-ray scattering techniques with Raman spectroscopy and Differential Scanning Calorimetry was conducted to correlate the structural changes from the conformational chain to the polymer crystal and mesoscale organization. Current research applications and the experimental combination of Raman spectroscopy with simultaneous SAXS/WAXS measurements coupled to a DSC is discussed. In particular, we show that in order to obtain the maximum benefit from simultaneously obtained high-quality data sets from different techniques, one should look beyond traditional analysis techniques and instead apply multivariate analysis. Data mining strategies can be applied to develop methods to control polymer processing in an industrial context. Crystallization studies of a PVDF blend with a fluoroelastomer, known to feature complex phase transitions, were used to validate the combined approach and further analyzed by MVA.

Amylose/cellulose nanofiber composites for all-natural, fully biodegradable and flexible bioplastics

Thermoplastic, polysaccharide-based plastics are environmentally friendly. However, typical shortcomings include lack of water resistance and poor mechanical properties. Nanocomposite manufacturing using pure, highly linear, polysaccharides can overcome such limitations. Cast nanocomposites were fabricated with plant engineered pure amylose (AM), produced in bulk quantity in transgenic barley grain, and cellulose nanofibers (CNF), extracted from agrowaste sugar beet pulp. Morphology, crystallinity, chemical heterogeneity, mechanics, dynamic mechanical, gas and water permeability, and contact angle of the films were investigated. Blending CNF into the AM matrix significantly enhanced the crystallinity, mechanical properties and permeability, whereas glycerol increased elongation at break, mainly by plasticizing the AM. There was significant phase separation between AM and CNF. Dynamic plasticizing and anti-plasticizing effects of both CNF and glycerol were demonstrated by NMR demonstrating high molecular order, but also non-crystalline, and evenly distributed 20 nm-sized glycerol domains. This study demonstrates a new lead in functional polysaccharide-based bioplastic systems.

Porous hollow TiO2 microparticles for photocatalysis: exploiting novel ABC triblock terpolymer templates synthesised in supercritical CO2

We report the synthesis of phase separated PMMA-b-PS-b-P4VP microparticles via RAFT-mediated dispersion polymerisation in scCO₂ and their use as a structure-directing agent for the fabrication of TiO₂ microparticles for photocatalysis.

Preparation and Performance of Supercritical Carbon Dioxide Thickener

The low sand-carrying problem caused by the low viscosity of supercritical carbon dioxide (SC-CO2) limits the development of supercritical CO2 fracturing technology. In this study, a molecular simulation method was used to design a fluorine-free solvent-free SC-CO2 thickener 1,3,5,7-tetramethylcyclotetrasiloxane (HBD). Simulations and experiments mutually confirm that HBD-1 and HBD-2 have excellent solubility in SC-CO2. The apparent viscosity of SC-CO2 after thickening was evaluated with a self-designed and assembled capillary viscometer. The results show that when the concentration of HBD-2 is 5 wt.% (305.15 K, 10 MPa), the viscosity of SC-CO2 increases to 4.48 mPa·s. Combined with the capillary viscometer and core displacement device, the low damage of SC-CO2 fracturing fluid to the formation was studied. This work solves the pollution problems of fluoropolymers and co-solvents to organisms and the environment and provides new ideas for the molecular design and research of SC-CO2 thickeners.

Synthesis of two-phase polymer particles in supercritical carbon dioxide

A simple method to synthesise phase-separated microparticles avoiding any control agents and post-polymerisation drying steps.

Monitoring morphology evolution within block copolymer microparticles during dispersion polymerisation in supercritical carbon dioxide: a high pressure SAXS study

Monitoring morphology development and evolution within block copolymer microparticles dispersed in supercritical CO₂ using in situ SAXS.

In situ crosslinking of nanostructured block copolymer microparticles in supercritical carbon dioxide

Nanostructured block copolymer microparticles crosslinked in situ during RAFT dispersion polymerisation in supercritical CO₂.

Thickening Supercritical CO₂ with π-Stacked Co-Polymers: Molecular Insights into the Role of Intermolecular Interaction

Vinyl Benzoate/Heptadecafluorodecyl acrylate (VBe/HFDA) co-polymers were synthesized and characterized as thickening agents for supercritical carbon dioxide (SC-CO₂). The solubility and thickening capability of the co-polymer samples in SC-CO₂ were evaluated by measuring cloud point pressure and relative viscosity. The molecular dynamics (MD) simulation for all atoms was employed to simulate the microscopic molecular behavior and the intermolecular interaction of co-polymer⁻CO₂ systems. We found that the introduction of VBe group decreased the polymer⁻CO₂ interaction and increased the polymer⁻polymer interaction, leading to a reduction in solubility of the co-polymers in SC-CO₂. However, the co-polymer could generate more effective inter-chain interaction and generate more viscosity enhancement compared to the Poly(Heptadecafluorodecyl) (PHFDA) homopolymer due to the driving force provided by π-π stacking of the VBe groups. The optimum molar ratio value for VBe in co-polymers for the viscosity enhancement of SC-CO₂ was found to be 0.33 in this work. The P(HFDA_0.67-co-VBe_0.33) was able to enhance the viscosity of SC-CO₂ by 438 times at 5 wt. %. Less VBe content would result in a lack of intermolecular interaction, although excessive VBe content would generate more intramolecular π-π stacking and less intermolecular π-π stacking. Both conditions reduce the thickening capability of the P(HFDA-co-VBe) co-polymer. This work presented the relationship between structure and performance of the co-polymers in SC-CO₂ by combining experiment and molecular simulations.

A facile route to bespoke macro- and mesoporous block copolymer microparticles

A facile and versatile strategy to fabricate macro- and mesoporous block copolymer microparticles with bespoke characteristics using supercritical CO₂.

One-pot synthesis of micron-sized polybetaine particles; innovative use of supercritical carbon dioxide

Well defined micron-sized polybetaine particles have been synthesised for the first time by precipitation polymerisation in a scCO₂/methanol mixture.

Block copolymer synthesis by controlled/living radical polymerisation in heterogeneous systems

We review the range of CLRP-controlled syntheses of block copolymer particles in dispersed systems, which are being exploited to create new opportunities for the design of nanostructured soft materials.