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In this study, a high-pressure-assisted photoinduced atom transfer radical polymerization (p ≤ 250 MPa) enabled the synthesis of ultra-high-molecular-weight polymers (UHMWPs) of up to 9 350 000 and low/moderate dispersity (1.10 < Đ < 1.46) in a co-solvent system (water/DMSO), without reaction mixture deoxygenation. [ABSTRACT FROM AUTHOR]

We show the remarkable effect of using static (DC) and alternating (AC) electric fields to control the free-radical polymerization of methyl methacrylate (MMA). The magnitude and/or frequency of the applied electric field (up to 154 kV cm−1) were found to control the molecular weight, dispersity, and stereochemistry of the produced polymers. [ABSTRACT FROM AUTHOR]

We report, for the first time, the metal-free green synthesis of linear poly(vinyl pyrrolidone) (PVP) homopolymers of molecular weight higher than 100 kg mol−1 and narrow dispersities via thermal and photo-induced free radical polymerisation carried out within alumina nanoporous membranes acting as “nanoreactors”. [ABSTRACT FROM AUTHOR]

In this paper, the high-pressure calorimetry was used to monitor the heat of the polymerization of bisphenol-A diglycidyl ether (DGEBA) mixed with a stoichiometric amount of aniline over a wide range of pressure (p = 0.1–350 MPa at T = 298.15 K). To the best of our knowledge, this is the first high-pressure calorimetric study of the reaction kinetics of the epoxy resin curing processes. The collected novel experimental data were analysed with two models: the original Kamal and its modified version taking into account the real monomer conversion, which provides insight into the progress of two subsequent non-catalyzed and catalyzed reactions occurring during the step growth polymerization. It was found that the determined rate constants are sensitive to pressure and model dependent, resulting in different activation volumes, which fall within the range from −16 cm3/mol to −26 cm3/mol. Interestingly, these values are similar to those reported for the epoxide ring-opening polymerization reaction, which changes in the range between −15 cm3/mol to −20 cm3/mol. In addition, the analysis of the high-pressure data revealed that the original Kamal model fails to describe kinetic curves obtained for the polymerization reaction, where the monomer conversion is far below 100%. Interestingly, such effects are considered to be due to the change in the mechanism of the reaction from mass to the diffusion-controlled regime. Here, we explicitly have shown that it has nothing to do with this phenomenon since after considering solely the real monomer conversion in the Kamal model fits, quality has been significantly improved. As a consequence, estimated rate constants are more reliable. Results presented herein clearly indicated that high-pressure experiments provide a new perspective to understand the progress of the classical reactions, as step-growth polymerization that has mainly been studied as a function of the chemical composition and temperature. Image 1 - High-pressure calorimetric data for step-growth polymerization (SGP) are presented - Original Kamal and modified version considering the monomer conversion were tested - Original model fails if the real monomer conversion is far below 100% - Rate constants are sensitive to pressure and model dependent - Activation volumes of catalyzed and non-catalyzed reactions in SGP are different [ABSTRACT FROM AUTHOR]

In this paper, we report 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) supported high-pressure approach enforcing Ring-Opening Polymerization (ROP) of γ-butyrolactone (GBL), that due to unfavorable thermodynamics and low ring strain, is considered as a hardly polymerizable monomer. Application of Broadband Dielectric Spectroscopy (BDS) allowed us to find optimal thermodynamic conditions to perform well-controlled and notably fast polymerization (even within 1 h!), avoiding undesired crystallization process. It was shown that by varying pressure and temperature conditions, we could control molecular weight, dispersity of recovered macromolecules, as well as rate and efficiency of the reaction that are significantly altered with respect to the reference process carried out at ambient conditions. Experiments performed at respectively very low temperature T = 233 K and low/moderate pressure (p = 75–250 MPa) and much higher temperatures (T = 248–268 K) and compressions (p = 1000 MPa) yielded poly(γ-butyrolactone) (PGBL) of tailored absolute molecular weight in moderate range M n = 2.8–15.0 (up to 30.3) kg/mol and narrow/moderate dispersity ranging from Đ = 1.12–1.89. What is more, the implementation of MALDI-TOF, GPC and DSC analyses, clearly indicated that as i) the time of reaction gets longer, ii) the amount of catalyst increases, iii) the temperature lowers, the content of cyclic products in produced polymers grows. This phenomenon influences the rheological properties (viscosity), foil formation ability (films) and cell culture proliferation features of the recovered macromolecules. Presented results open a highly effective and repeatable route to produce PGBL via pressure-assisted ROP and indicate the possibility of tuning properties of this polymer by varying concentration of cycles or eventual block copolymerization with other biorelevant monomers to meet the expectations of the biotechnological industry. [Display omitted] • Organocatalyzed high-pressure assisted γ-butyrolactone Ring-Opening Polymerization. • Well-defined macromolecules (M n up to 30.3 kg/mol; low to moderate Đ = 1.12–1.89). • External catalytic effect of high pressure: reduced reaction time; increased yield. • Monitoring the polymerization progress in situ using BDS technique. • Analysis: NMR, GPC, MALDI, DSC, SEM, rheology, cytotoxicity, cell proliferation. [ABSTRACT FROM AUTHOR]