Catalytic Chain Transfer Polymerization Research Articles

The Effect of Macromonomer Surfactant Microstructure on Aqueous Polymer Dispersion and Derived Polymer Film Properties.

Water-borne coatings were prepared from poly(methyl methacrylate-co-butyl acrylate) latexes using different methacrylic acid containing macromonomers as stabilizers, and their physical properties were determined. The amphiphilic methacrylic acid macromonomers containing methyl, butyl, or lauryl methacrylate as hydrophobic comonomers were synthesized via catalytic chain transfer polymerization to give stabilizers with varying architecture, composition, and molar mass. A range of latexes of virtually the same composition was prepared by keeping the content of methacrylic acid groups during the emulsion polymerization constant and by only varying the microstructure of the macromonomers. These latexes displayed a range of rheological behaviors: from highly viscous and shear thinning to low viscous and Newtonian. The contact angles of the resulting coatings ranged from very hydrophilic (<10°) to almost hydrophobic (88°), and differences in hardness, roughness, and water vapor sorption and permeability were found.

Vat photopolymerization using catalytic chain transfer polymerization (CCTP) derived reactive oligomers to influence mechanical properties

ω-Vinyl terminated reactive oligomers of 2-ethylhexyl methacrylate and poly(ethylene glycol)methacrylate (PEGMA) were synthesized via CCTP and subsequent addition–fragmentation chain transfer (AFCT) polymerization.

Screening of Oligomeric (Meth)acrylate Vaccine Adjuvants Synthesized via Catalytic Chain Transfer Polymerization.

This report details the first systematic screening of free-radical-produced methacrylate oligomer reaction mixtures as alternative vaccine adjuvant components to replace the current benchmark compound squalene, which is unsustainably sourced from shark livers. Homo-/co-oligomer mixtures of methyl, butyl, lauryl, and stearyl methacrylate were successfully synthesized using catalytic chain transfer control, where the use of microwave heating was shown to promote propagation over chain transfer. Controlling the mixture material properties allowed the correct viscosity to be achieved, enabling the mixtures to be effectively used in vaccine formulations. Emulsions of selected oligomers stimulated comparable cytokine levels to squalene emulsion when incubated with human whole blood and elicited an antigen-specific cellular immune response when administered with an inactivated influenza vaccine, indicating the potential utility of the compounds as vaccine adjuvant components. Furthermore, the oligomers' molecular sizes were demonstrated to be large enough to enable greater emulsion stability than squalene, especially at high temperatures, but are predicted to be small enough to allow for rapid clearance from the body.

Reversible bond formation via sulfur free reversible addition fragmentation in photo-3D printing

An addition-fragmentation monomer (AFM) has been used as a crosslinker in photopolymerization-based 3D printer resins in order to try and reduce shrinkage due to polymerisation. This results in reversible network formation via photo crosslinking with reversible covalent bond formation to effect mechanical performance. The 3D printing conditions were optimized with regards to print quality, print speed, etc. The AFM was synthesized via catalytic chain transfer polymerization (CCTP) and characterized using NMR and size exclusion chromatography (SEC). The incorporation of the AFM as a crosslinker allows for rapid reversible covalent bond formation during network formation in 3D photopolymerization printing resulting in a reduction in both polymerisation shrinkage and stress higher molecular weight crosslinkers lead to less shrinkage and reversible bond formation to less stress build up. Curing was monitored via photo-rheology and Fourier Transform Infrared Spectroscopy (FT-IR). At lower contents of AFM, the mechanical properties (strength and Young’s modulus) are improved without compromising material properties, printing conditions and curing time. At higher AFM content, the kinetic analysis of the photopolymerization reaction shows a reduced final conversion of the vinylic bonds along with a delay of the gel point. The thermal and mechanical properties were evaluated with incorporation of different concentrations of AFM added to the resin formulations.

Synthesis of poly(methyl methacrylate)-b-polyethylene (PMMA-b-PE) block copolymers via conventional emulsion polymerization

Block copolymers can be obtained by combining catalytic chain transfer polymerization (CCTP) and conventional free radical emulsion polymerization of ethylene.

Facile Synthesis of Functionalised Hyperbranched Polymers for Application as Novel, Low Viscosity Lubricant Formulation Components.

A novel, previously unreported, method for synthesising hyperbranched (HB) materials is detailed. Their use as additives to produce lubricant formulations that exhibit enhanced levels of wear protection and improved low-temperature oil viscosity and flow is also reported. The lubricant formulations containing HB additives were found to exhibit both significantly lower viscosities and improved in-use film-forming properties than the current industry standard formulations. To achieve this, alkyl methacrylate oligomers (predominantly dimers and trimers) were synthesised using catalytic chain transfer polymerisation. These were then used as functional chain transfer agents (CTA) to control the polymerisation of divinyl benzene (DVB) monomers to generate highly soluble, high polydispersity HB polymers. The level of dimer/trimer purification applied was varied to define its influence on both these HB resultant structures and the resultant HB additives’ performance as a lubricant additive. It was shown that, while the DVB acted as the backbone of the HB, the base oil solubility of the additive was imparted by the presence of the alkyl chains included in the structure via the use of the oligomeric CTAs.

Novel Strategy for the Synthesis of Polymer/Pigment Hybrid Latex via Sulfur-Free RAFT-Mediated Emulsion Polymerization

Reversible addition–fragmentation chain transfer (RAFT) emulsion polymerization is a powerful tool for polymer encapsulation of pigment nanohybrids. Conventional RAFT emulsion polymers, however, contain sulfur residues that contribute to undesired odor and deleterious effects on final materials. Our strategy relies on an amphiphilic macromonomer poly(methacrylic acid-co-methyl methacrylate) P(MAA-co-MMA) with an ω-unsaturated end group synthesized in situ via cobalt(II)-mediated catalytic chain transfer polymerization (CCTP) at the surface of C.I. Pigment Blue 15:3 (PB) particles. Subsequently, these macromonomers are used as the living points to mediate the in situ sulfur-free RAFT (SF-RAFT) emulsion polymerization of monomers (butyl methacrylate (BMA) and butyl acrylate (BA)). It was found that a well-controlled polymerization process was achieved by semibatch SF-RAFT emulsion polymerization on the PB surface, as evidenced by the smooth increase in the molecular weight of polymer chains as the polymerization progressed and by transmission electron microscopy (TEM) results. Due to the sealing effect, these polymer/PB hybrid particles exhibited excellent colloidal stability in the aqueous phase. More importantly, film-forming hybrid particles with a soft P(BMA-co-BA) shell were successfully prepared in this work, which suggested that SF-RAFT-mediated polymerization may offer a useful alternative approach to traditional RAFT emulsion polymers for the preparation of organic/inorganic nanohybrids.

Resolving long-chain branch formation in tandem catalytic coordinative chain transfer polymerization of ethylene via thermal analysis

Resolving long-chain branch formation in tandem catalytic coordinative chain transfer polymerization of ethylene via thermal analysis

Synthesis of Betaine Copolymer for Surface Modification of Cotton Fabric by Enhancing Temperature-Sensitive and Anti-Protein Specific Absorption Performance.

The growth and reproduction of microorganisms on fabrics could not only affect the wearability of textiles but also cause harm to human health, and it is an important problem that should be solved to reduce the adsorption and growth of microorganisms on the surface of the fabric. A series of ω-vinyl betaine copolymers were synthesized by catalytic chain transfer polymerization (CCTP) and were modified by mercapto-vinyl click chemistry to synthesize silane-modified betaine copolymers, which were used to treat the cotton fabric. The hydrophilic–hydrophobic transition performance and anti-protein specific adhesion performance of cotton fabric with the betaine copolymer were systematically investigated. The copolymer was confirmed to be successfully finished on the cotton fabric via 1H–NMR and FTIR. The cotton fabric, which was treated by the betaine copolymer, presented temperature response performance in the range of 30–55 °C and had excellent anti-protein adsorption performance. The treated fabric had the best temperature-sensitive and anti-protein specific absorption performance among all the specimens when the mass fraction of G06B in DMAPS was 6 wt.%.

Block Copolymers Based on Ethylene and Methacrylates Using a Combination of Catalytic Chain Transfer Polymerisation (CCTP) and Radical Polymerisation

AbstractTwo scalable polymerisation methods are used in combination for the synthesis of ethylene and methacrylate block copolymers. ω‐Unsaturated methacrylic oligomers (MMAn) produced by catalytic chain transfer (co)polymerisation (CCTP) of methyl methacrylate (MMA) and methacrylic acid (MAA) are used as reagents in the radical polymerisation of ethylene (E) in dimethyl carbonate solvent under relatively mild conditions (80 bar, 70 °C). Kinetic measurements and analyses of the produced copolymers by size exclusion chromatography (SEC) and a combination of nuclear magnetic resonance (NMR) techniques indicate that MMAn is involved in a degradative chain transfer process resulting in the formation of (MMA)n‐b‐PE block copolymers. Molecular modelling performed by DFT supports the overall reactivity scheme and observed selectivities. The effect of MMAn molar mass and composition is also studied. The block copolymers were characterised by differential scanning calorimetry (DSC) and their bulk behaviour studied by SAXS/WAXS analysis.

Block Copolymers Based on Ethylene and Methacrylates Using a Combination of Catalytic Chain Transfer Polymerisation (CCTP) and Radical Polymerisation.

Two scalable polymerisation methods are used in combination for the synthesis of ethylene and methacrylate block copolymers. ω‐Unsaturated methacrylic oligomers (MMAn) produced by catalytic chain transfer (co)polymerisation (CCTP) of methyl methacrylate (MMA) and methacrylic acid (MAA) are used as reagents in the radical polymerisation of ethylene (E) in dimethyl carbonate solvent under relatively mild conditions (80 bar, 70 °C). Kinetic measurements and analyses of the produced copolymers by size exclusion chromatography (SEC) and a combination of nuclear magnetic resonance (NMR) techniques indicate that MMAn is involved in a degradative chain transfer process resulting in the formation of (MMA)n‐b‐PE block copolymers. Molecular modelling performed by DFT supports the overall reactivity scheme and observed selectivities. The effect of MMAn molar mass and composition is also studied. The block copolymers were characterised by differential scanning calorimetry (DSC) and their bulk behaviour studied by SAXS/WAXS analysis.

Amphiphilic Statistical Copolymers from Catalytic Chain Transfer as Reactive Surfactants in Emulsion Polymerization

Statistical copolymers of methacrylic acid (MAA) and methyl methacrylate (MMA), butyl methacrylate (BMA), or lauryl methacrylate (LMA) were synthesized via cobalt(II)-mediated catalytic chain transfer polymerization (CCTP) and used as macromonomeric stabilizers in the emulsion polymerization of MMA. By varying the composition, length, and concentration of the macromonomers, we were able to tune the particle size, molar mass, and rheological behavior of the latexes. Most latexes stabilized with macromonomers containing BMA and LMA showed rheological properties such as small yield stress and shear thinning behavior similar to those of binders for coating applications.

Controlling the Particle Size in Surfactant-Free Latexes from ω-Propenyl Oligomers Obtained through Catalytic Chain Transfer Polymerization

Controlling the Particle Size in Surfactant-Free Latexes from ω-Propenyl Oligomers Obtained through Catalytic Chain Transfer Polymerization

Mechanistic study on the metallocene-based tandem catalytic coordinative chain transfer polymerization for the synthesis of highly branched polyolefins

Creation and control of long-chain branches (LCBs) in coordination polymerization of olefins is an enduring focus of research in both academia and industry. We have recently introduced a tandem catalytic coordinative chain transfer polymerization reaction where upon the concerted function of the polymerization catalyst, the chain transfer agent (CTA), and the displacement catalyst, a highly branched microstructure can be formed. Here we introduce a new tandem catalytic system using Et(Ind)2ZrCl2 as the polymerization catalyst. Despite the optimal reaction temperature for the cooperative function of catalyst components is lower than the ideal temperature for the productivity of the metallocene catalyst, the formation of branches is evident from the decrease and broadening of melting peaks and deviation of rheological properties from characteristic behavior of linear chains in cole–cole plots. Surprisingly, the introduction of the displacement catalyst in CCTP of 1-hexene resulted in low yields and too short polymer chains. Accordingly, we elaborate on the mechanism of this reaction, specifically, we show how the optimal conditions for the (BiPy)2FeEt2 displacement catalyst depend on the monomer type. Namely, the presence of a β–agostic interaction in the bimetallic intermediate formed by the CTA and the displacement catalyst alters the structure of the latter when monomers longer than ethylene are present. This report suggests that our proposed method for the synthesis of branched polyolefins has a great potential for being used in the currently available industrial plants that employ classic metallocene catalysts.

Optimal radiation shielding capacity and thermal properties of poly(methyl methacrylate) films enhanced with different metal complexes

Samples of pure poly(methyl methacrylate) (PMMA) and PMMA enhanced with metal complexes of Zn, Cd, and Hg were synthesized via catalytic chain transfer polymerization. Structural analysis, by means of XRD, showed the amorphous nature of the studied samples which meant high homogenous dissolution of the metals (Zn, Cd and Hg) into the polymer matrix. Density values increased linearly with respect to atomic radius of the incorporated metals. Addition of such elements causes an increase in mass attenuation coefficients and a remarkable decrease in the Half Value Layer (HVL) values, in comparison to existing standard shielding materials. Thermal studies by DSC indicated highly homogenous internal structure of the studied samples, with slight decrease in the Tg value when introducing metals due to heterogeneous nucleation agent role of the Cd, Zn and Hg. All observations and results suggest the studied materials to be used as promising and proper aprons for medical radiation shielding applications.

Evaluation of Polymethyl Methacrylate Sheets as a Radiation Shielding Material

Polymethyl methacrylate (PMMA) samples were previously prepared by catalytic chain transfer polymerization via metal carbazone of Zn, Cd, and Hg. The density change of PMMA with different metal carbazone complex reveals that Cd cation is denser than the others. The thermal stability of specimens, their hardness as well as their shielding properties has been investigated to ensure that the validity of these materials for application to the problem of the permanent disposal of nuclear wastes. The results indicated that PMMA samples which prepared through the present mechanism have good thermal stability and hardness, especially in case of Cd metal. The shielding parameters such as mass attenuation coefficients (μ/ρ) and half value layer (HVL) values have been measured using NaI(Tl) detector and the variation of shielding parameters are discussed taking into consideration the effect of photon energy and different metal carbazone complex addition on these parameters. The addition of those elements causes an increase in mass attenuation coefficient, while HVL values were decreased. The obtained results give further support to the investigated material to be used as a promising and proper shielding material.

Achieving Microparticles with Cell‐Instructive Surface Chemistry by Using Tunable Co‐Polymer Surfactants

AbstractA flow‐focusing microfluidic device is used to produce functionalized monodisperse polymer particles with surface chemistries designed to control bacterial biofilm formation. This is achieved by using molecularly designed bespoke surfactants synthesized via catalytic chain transfer polymerization. This novel approach of using polymeric surfactants, often called surfmers, containing a biofunctional moiety contrasts with the more commonly employed emulsion methods. Typically, the surface chemistry of microparticles are dominated by unwanted surfactants that dilute/mask the desired surface response. Time of flight secondary ion mass spectrometry (ToF‐SIMS) analysis of particles demonstrates that the comb‐graft surfactant is located on the particle surface. Biofilm experiments show how specifically engineered surface chemistries, generated by the surfactants, successfully modulate bacterial attachment to both polymer films, and microparticles. Thus, this paper outlines how the use of designed polymeric surfactants and droplet microfluidics can exert control over both the surface chemistry and size distribution of microparticle materials, demonstrating their critical importance for controlling surface‐cell response.

Catalytic Chain Transfer Polymerization to Functional Reactive End Groups for Controlled Free Radical Growth

Alkoxyamine-functionalized silane functions as a chain transfer reagent in ethylene polymerization catalyzed by cationic palladium diimine complexes, without significant adverse effects in producti...

Polymerisable surfactants for polymethacrylates using catalytic chain transfer polymerisation (CCTP) combined with sulfur free-RAFT in emulsion polymerisation

Statistical copolymers of methacrylic acid and methyl methacrylate were synthesised via free radical catalytic chain transfer polymerisation (CCTP) in emulsion to form a hydrophilic emulsifier/surfactant. The vinyl-terminated oligomers were in turn utilised as chain transfer agents, with no further purification, for the formation of diblock copolymers with butyl and methyl methacrylate which constitutes the emulsifier via sulfur-free reversible addition–fragmentation chain transfer polymerisation (SF-RAFT). In turn these polymers were solubilized with various concentrations of ammonium hydroxide and utilised in the surfactant-free emulsion polymerization of butyl methacrylate using persulfate initiators, which also stabilized the polymer particles with observed no coagulation, with solid contents as high as 40%.

Recent advances in catalytic chain transfer polymerization of isobutylene: a review.

This review presents the development of highly reactive polyisobutylene (HRPIB), a major commercial intermediate toward fuel and lubricant additives. Recent years have witnessed very substantial advances in the catalytic chain transfer polymerization (CCTP) of isobutylene/industrial Raffinate-1 (C4 Raffinate) to produce HRPIB, particularly in nonpolar solvents at elevated temperatures. The main subjects of this review are cationic polymerization of isobutylene, progress in HRPIB research and existing challenges, and recent advances of CCTP. New initiating/catalyst systems based on ionic liquids with Lewis acids are detailed, and this approach may open new views in the synthesis of HRPIB. Some current developments in CCTP of industrial Raffinate-1 and mechanistic studies are also described. This review strongly supports that the hydrocarbon soluble Lewis acid·ether (LA·ether) complex catalyzed CCTP will become the most popular technique for preparing HRPIB and could replace the traditional BF3 catalyzed industrial method.