Monomer Reactivity Ratios Research Articles

Effect of Solvents on the Performance and Structure of Polymethylacrylimide Aerogels.

Solvent effects play a critical role in solution polymerization, especially in free radical polymerization, where they influence both monomer-solvent interactions and the resulting polymer structure. In this study, polymethacrylimide (PMI) aerogels were synthesized via freeze-drying using dimethylformamide (DMF), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO) as solvents. The effects of monomer reactivity ratios, monomer distribution, and solvent-monomer interactions on the shrinkage, bulk density, pore size, and compressive properties of the aerogels were investigated. Results demonstrated that solvent choice significantly impacted the polymerization process, leading to variations in the structure and properties of the final aerogels. Notably, aerogels synthesized in DMSO, the most polar solvent, exhibited the lowest shrinkage (33.98%), highest density (0.1582 g·cm-3), and highest compressive stress (1695.48 kPa at 70% strain). These findings underscore the importance of solvent selection in controlling the microstructure and enhancing the mechanical performance of PMI aerogels.

Synthesis and Characterization of Statistical and Block Copolymers of n-Hexyl Isocyanate and 3-(Triethoxysilyl) Propyl Isocyanate via Coordination Polymerization.

Well-defined statistical copolymers of n-hexyl isocyanate, HIC, and 3-(triethoxysilyl)propyl isocyanate, TESPI, were synthesized via coordination polymerization mechanism, employing a chiral half-titanocene complex as initiator. The monomer reactivity ratios of the statistical copolymers were calculated using linear graphical methods and the computer program COPOINT in the frame of the terminal model. The molecular and structural characteristics of the copolymers were also calculated. The kinetics of the thermal decomposition of the statistical copolymers was studied by Thermogravimetric Analysis, TGA, and Differential Thermogravimetry, DTG, and the activation energy of this process was calculated employing several theoretical models. In addition, block copolymers constituted from PHIC and PTESPI blocks were synthesized by sequential coordination polymerization. All samples were characterized by nuclear magnetic resonance, NMR, spectroscopy and size exclusion chromatography, SEC. The thermal stability of the blocks was also studied by TGA and DTG and compared to the corresponding statistical copolymers.

Biobased Copolymers via Cationic Ring-Opening Copolymerization of Levoglucosan Derivatives and ε-Caprolactone.

Simultaneous ring-opening copolymerization is a powerful strategy for the synthesis of highly functional copolymers from different types of cyclic monomers. Although copolymers are essential to the plastics industry, environmental concerns associated with current fossil-fuel-based synthetic polymers have led to an increasing interest in the use of renewable feedstock for polymer synthesis. Herein, we report a scalable synthetic platform to afford unique polysaccharides with different pendant functional groups from biomass-derived levoglucosan and ε-caprolactone via cationic ring-opening copolymerization (cROCOP). Biocompatible and recyclable bismuth triflate was identified as the optimal catalyst for cROCOP of levoglucosan. Copolymers from tribenzyl levoglucosan and ε-caprolactone, as well as from tribenzyl and triallyl levoglucosan, were successfully synthesized. The tribenzyl levoglucosan monomer composition ranged from 16% to 64% in the copolymers with ε-caprolactone and 22% to 79% in the copolymers with triallyl levoglucosan. The allylic levoglucosan copolymer can be utilized as a renewably derived scaffold to modify copolymer properties and create other polymer architectures via postpolymerization modification. Monomer reactivity ratios were determined to investigate the copolymer microstructure, indicating that levoglucosan-based copolymers have a gradient architecture. Additionally, we demonstrated that the copolymer glass transition temperature (Tg, ranging from -44.3 to 33.8 °C), thermal stability, and crystallization behavior could be tuned based on the copolymer composition. Overall, this work underscores the utility of levoglucosan as a bioderived feedstock for the development of functional sugar-based copolymers with applications ranging from sustainable materials to biomaterials.

Stereospecific radical polymerization of methacrylate bearing oxazolidone structure and improvement of glass transition temperature of urethane methacrylate copolymers

AbstractWe synthesized the novel methacrylate monomer bearing an oxazolidone structure (M1) and performed radical polymerization of M1 by traditional procedures. The glass transition temperature (Tg) of the obtained polymer (P1) was a significantly high value compared to that of poly(methyl methacrylate) and typical poly(urethane methacrylate)s. The copolymers of M1 and monofunctional urethane methacrylate derived from 2‐hydroxyethyl methacrylate and phenyl isocyanate (M2) exhibited a linear rise of the Tg values depending on the composition ratio of M1. The NMR analysis and the estimation of monomer reactivity ratio and Q–e values suggested that the improvement of glass transition temperature resulted from a stereoregularity, meaning a syndiotacticity of the copolymers improved with increasing the composition ratio of M1. Furthermore, the thermal curing reaction of M1 or M2 with bifunctional urethane acrylate successfully proceeded, then the Tg value of the cured product from M1 was much higher than that from M2.

Statistical Copolymers of N-Vinylpyrrolidone and 2-Chloroethyl Vinyl Ether via Radical RAFT Polymerization: Monomer Reactivity Ratios, Thermal Properties, and Kinetics of Thermal Decomposition of the Statistical Copolymers.

The radical statistical copolymerization of N-vinyl pyrrolidone (NVP) and 2-chloroethyl vinyl ether (CEVE) was conducted using the Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization technique, employing [(O-ethylxanthyl)methyl]benzene (CTA-1) and O-ethyl S-(phthalimidylmethyl) xanthate (CTA-2) as the Chain Transfer Agents (CTAs), leading to P(NVP-stat-CEVE) products. After optimizing copolymerization conditions, monomer reactivity ratios were estimated using various linear graphical methods, as well as the COPOINT program, which was applied in the framework of the terminal model. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the monomers' mean sequence lengths. Thermal properties of the copolymers were studied by Differential Scanning Calorimetry (DSC) and kinetics of their thermal degradation by Thermogravimetric Analysis (TGA) and Differential Thermogravimetry (DTG), applying the isoconversional methodologies of Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS).

Development of a chemometric approach to improve the accuracy of copolymer sequence information obtained from pyrolysis gas-chromatography mass-spectrometry data

Number-average copolymer sequence length information can be obtained by pyrolysis-gas chromatography (Py-GC) by comparing the ratios of formed oligomers (i.e. dimers and trimers). The formation constants of the oligomers and their detection efficiency are not constant for all fragments, however. This can lead to unrepresentative peak ratios in the chromatogram. In these cases, calibration with an external method (e.g. NMR) is required. In this work, we introduce an algorithm that improves the copolymer sequence accuracy yielded from chromatograms with unrepresentative peak areas. The algorithm even functions in cases where oligomer data is missing as the rate of formation of certain oligomers is too low to detect them. One Py-GC measurement and one NMR measurement are required to train the developed algorithm for the determination of average monomer reactivity ratios and relative pyrolysis constants. Afterwards, Py-GC measurements of copolymers containing the same monomers, albeit with different compositions, can be corrected using the previously estimated constants. The algorithm was tested on various styrene-acrylate copolymers, yielding more accurate sequence information, even when limited oligomer information was available.

Machine learning approach to polymer reaction engineering: Determining monomers reactivity ratios

In copolymerization, the monomers' reactivity ratios play an important role in shaping the final copolymer properties. Thus, the knowledge of reactivity ratio is essential to the polymer reaction engineering. However, the experimental methods of determining reactivity ratios are laborious and require many repetitions and testing at different compositions. Therefore, computational methods for determining the reactivity ratios based on the chemical structures of the reactants have attracted significant attention. Here, we demonstrate how machine learning enables the prediction of comonomers reactivity ratios based on the molecular structure of monomers. We combined multi-task learning, multi-inputs, and one of the state-of-the-art machine learning model – Graph Attention Network – to build a model capable of predicting reactivity ratios based on the monomers’ chemical structures. We found that the interpretable characteristics of Multi-Input-Multi-Output Graph Attention Network, along with its capability to learn chemical features facilitates the accurate prediction of the reactivity ratios. Such a predictive tool can be used in combination with macroscopic kinetic models to design new copolymers.

Visible light‐catalyzed living cationic homopolymerization and copolymerization of isobutyl vinyl ether: Characteristics and mechanism

AbstractOn the basis of synthesizing a highly efficient chain‐transfer agent ethyl (1‐isobutoxyethyl) carbonotrithioate(CTA), living cationic polymerization of isobutyl vinyl ether (IBVE) was successfully initiated by visible light catalysis. The random copolymerization of isobutyl vinyl ether and propyl vinyl ether (PVE), cyclohexyl vinyl ether (CyVE), and 2‐chloroethyl vinyl ether (CEVE) was achieved on the basis of investigating the reactivity ratios of vinyl ether monomers. The influence of photocatalyst (PC) concentration and wavelength on the copolymerizations was investigated. It was found that high PC concentration results in a fast polymerization rate. The wavelength of the blue LED was most suitable for this reaction system. This photocatalytic reaction provides a new way for molecular design of cationic polymerization.

Investigation of the Conditions for the Synthesis of Poly(3,4-ethylenedioxythiophene) ATRP Macroinitiator

One of the most widely used conductive polymers in the growing conductive polymer industry is poly(3,4-ethylenedioxythiophene) (PEDOT), whose main advantages are good thermal and chemical stability, a conjugated backbone, and ease of functionalization. The main drawback of PEDOT for use as wearable electronics is the lack of stretchable and self-healing properties. This can be overcome by grafting PEDOT with flexible side branches. As pure PEDOT is highly stable and grafting would not be possible, a new bromine-functionalized thiophene derivative, 2-(tiophen-3-yl) ethyl 2-bromo-2-methylpropanoate (ThBr), was synthesized and copolymerized with EDOT for the synthesis of a poly(EDOT-co-ThBr) ATRP macroinitiator. After the synthesis of the macroinitiator, flexible polymers could be introduced as side branches by atom-transfer radical polymerization (ATRP) to modify mechanical properties. Before this last synthesis step, the conditions for the synthesis of the ATRP macroinitiator should be investigated, as only functionalized units can function as grafting sites. In this study, nine new copolymers with different monomer ratios were synthesized to investigate the reactivity of each monomer. The ratios used in the different syntheses were ThBr:EDOT = 1:0.2, 1:0.4, 1:0.6, 1:0.8, 1:1, 0.8:1, 0.6:1, 0.4:1, and 0.2:1. In order to determine the effect of reaction time on the final properties of the polymer, macroinitiator synthesis at a 1:1 ratio was carried out at different time periods: 8 h, 16 h, 24 h, and 48 h. The obtained products were characterized by different techniques, and it was found that polymerizations longer than 24 h yielded practically insoluble macroinitiators, thus limiting its further application. Reactivity ratios of both monomers were found to be similar and close to 1, making the copolymerization reaction symmetrical and the obtained macroinitiators almost random copolymers.

Synthesis of superhydrophilic Gradient-Like Copolymers: Kinetics of the RAFT copolymerization of methacryloyloxyethyl phosphorylcholine with PEO methacrylate

Brush copolymers containing PEO side chains and zwitterionic units of 2-methacryloyloxyethyl phosphorylcholine (MPC) were synthesized by RAFT copolymerization with an especial attention to compositional microstructure of the copolymers. Two complementary methods – size exclusion chromatography (SEC) and 1H NMR spectroscopy – were used to study the kinetics of the RAFT copolymerization of MPC (M1) and the macromonomer poly(ethylene oxide) methyl ether methacrylate with medium-length PEO chain (PEOMEMA, M2) in methanol–water mixed solutions. Analysis of the reaction mixtures by the two methods allowed concluding that in mixed solutions of methanol and water, every molecule of MPC carries about 15 molecules of water as an integral part of the monomer. Monomer reactivity ratios calculated by the method of Meyer and Lowry were r1 = 2.48 and r2 = 0.40. The dependences of the copolymer composition on monomer conversion determined experimentally and calculated by the terminal model of free-radical copolymerization differed significantly, demonstrating the specific impact of the mechanism of RAFT on the distribution of copolymer compositions. The copolymers p(MPC-co-PEOMEMA) possessed strongly expressed gradient microstructure, and were characterized by moderately low dispersity (Ð < 1.3). The copolymers showed evident superhydrophilicity with a water contact angle of about 7° and, like pMPC, exhibited cononsolvency in water–ethanol mixed solutions.

Synthesis and Properties of Polyol Copolymer with Alternating Methacrylate-Vinyl Ether Backbone.

Radical polymerization of a tailored diphenylsilane-bridged bi-functional monomer consisting of methacrylate and vinyl ether moieties is conducted in diluted monomer concentration, in which both two moieties are consumed at almost the same rate despite their huge difference in monomer reactivity ratio. The vinyl ether content in the backbone is quantified as 45% by 1 H NMR after removal of the silane bridge. Since vinyl ether alone cannot be polymerized in such radical polymerization, it should be incorporated in an alternating fashion with methacrylate into the copolymer main chain. The cleavage of silane bridge also yields a series of polyol materials composed of ethylene glycol monovinyl ether (EGVE) and hydroxyethyl methacrylate (HEMA), and the EGVE content in the backbone can be regulated from 45% to 18% by increasing the bi-functional monomer concentration. Interestingly, although containing more than 50% HEMA units, the alternating copolymer exhibits new properties totally different from poly(HEMA), but more similar to poly(EGVE), e.g., good water solubility and a markedly low glass transition temperature (Tg ) of -31°C, which is attributed to the major HEMA-EGVE repeating unit that replaced HEMA-HEMA consecutive segments so that the properties of poly(HEMA) such as 95°CTg are completely altered.

Novel synthesized amide-incorporating copolymeric surfactants based on natural wastes as petro-dispersing agents: Design, synthesis, and characterizations

New cationic copolymeric surfactants were synthesized based on the fatty acid obtained from Juagafa seed wastes, which gave an appropriate yield of lauric acid, which upon esterification and reduction processes was converted to lauryl alcohol. Through the reaction of lauryl alcohol with methacrylic acid (MAA) in the presence of N,N′-dicyclohexylcarbadiimide (DCC), lauryl methacrylate (LMA, as a starting monomer) was obtained. A series of copolymerization feeds between lauryl methacrylate and methacrylic acid in different molar ratios initiated by benzoyl peroxide (BP) were carried out. Also, the obtained data from 1H NMR for the different molar ratios of the poly(LMA-co-MAA) were utilized to estimate the monomer reactivity ratio. The synthesized poly(LMA-co-MAA) with different molar ratio was modified by direct amidation with N,N'-dimethyl-1,3-propanediamine. The amidated copolymers (PA1-5) were quaternized with methyl and ethyl iodides to obtain the corresponding cationic copolymeric surfactants (PSM and PSE). The chemical structures of the prepared compounds were confirmed by FT-IR and 1H NMR analysis. The critical micelle concentrations of the prepared cationic copolymeric surfactants were investigated. Also, the studies of petroleum-collecting and dispersing properties showed that copolymeric surfactants (PSE) have promised effects than PSM ones, especially in sea water and diluted form, and the best molar ratio that gave excellent dispersion of petroleum is PSM-3 and PSE-3.

Novel cationic copolymeric surfactants bearing imidazole moiety as petro-dispersing / petro-collecting agents: Synthesis, surface activity and characterization

Novel cationic copolymeric surfactants were designed and synthesized by the quaternization of the copolymer. The synthesized route passes through a two-step reaction, initially including the copolymerization of methacrylic acid (MAA) with 1-vinylimidazole (VIM), followed by the quaternization of the nitrogen atom in imidazole ring present in the obtained poly(VIM-co- MAA) (AI1-5)with different molar ratios, with methyl- and ethyl iodide, respectively to form AISM1-5 and AISE1-5. The chemical structure of the prepared copolymers and cationic polymeric surfactants was confirmed using different spectroscopic techniques such as FT-IR and 1H NMR. The surface-active properties of the synthesized cationic polymeric surfactants were examined. Finema-Ross (F-R) and Kelen-Tudos (K-T) methods were studied from the elemental analysis data, which included the evaluation of the nitrogen content (N%) in prepared copolymers. The monomer reactivity ratios are r1 = 0.157; r2 = 0.966 by F-R and r1 = 0.122; r2 = 0.995) by K-T methods that showed the value of r1r2 is less than the unity (0.152), which indicates the random distribution. The results showed that in sea water, AISE4 is the most distinctive as a petro-dispersant in undiluted form. As well, in diluted and undiluted forms of AISE4, the best petro-collecting capacity is observed on the surface of distilled water.

Synthesis and characterization of (allylamine hydrochloride-vinyl sulfonic acid) copolymer and determination of monomer reactivity ratios

Synthesis and characterization of (allylamine hydrochloride-vinyl sulfonic acid) copolymer and determination of monomer reactivity ratios

Homopolymer-block-Alternating Copolymers Composed of Acrylamide Units: Design of Transformable Divinyl Monomers and Sequence-Specific Thermoresponsive Properties.

In this work, we synthesized an acrylamide-based terpolymer that is a block copolymer composed of an AB alternating copolymer and a C homopolymer. The key to the unprecedented achievement is rational design of an acrylate-acrylamide divinyl monomer carrying CF3-substituted salicylic acid ester bonds (AAm-CF3) to realize the efficient and selective cyclopolymerization as well as the quantitative transformation of the resultant cyclorepeating units. The selectivity in the cyclopolymerization and the pendant transformation ability were evaluated through reactivity ratios of the corresponding model monomers and quantitative aminolysis reactions of the model compound. The cyclopolymerization via the photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) process with a macrochain-transfer agent and subsequent aminolysis reaction afforded the homopolymer-block-alternating copolymer. The sequence-controlled terpolymer exhibited a very unique thermal response behavior in water that was strikingly different from the corresponding sequence-uncontrolled terpolymers, such as homopolymer-block-statistical copolymers and all statistical terpolymers, despite the fact that the structure cannot be distinguished by 1H NMR.

Novel Methacrylamide Polymers Based on Thiazole and Styrene: A Study on Synthesis, Characterization, and Determination of Monomer Reactivity Ratios

In this study, firstly, a thiazole methacrylamide (TMAAm) monomer was synthesized from methacryloyl chloride with 2-aminothiazole. Later on, a series of copolymers of 2-thiazole methacrylamide (TMAAm) with styrene (St) using strange compositions in the feed has been prepared in solution via radical at 70 oC with AIBN as initiator. The structure of the copolymers was elucidated by FT-IR, 1H-NMR, and 13C-NMR spectroscopy methods. The compositions of the copolymers were determined from the nitrogen (N) difference according to the elemental analysis results. Monomer reactivity ratios; The rTMAAm and rSt, Fineman-Ross (FR), Kelen-Tüdös (KT) linear methods, and the error method model in non-linear variables were calculated with the computer program RREVM. The molecular weights and heterogeneity indices of the copolymers were determined by the GPC method. The thermal stability of the copolymers was investigated by thermogravimetry (TG) measurements.

Determination of monomer reactivity ratios from a single sample using multivariate analysis of the 1H NMR spectra of poly[(methyl methacrylate)-co-(benzyl methacrylate)

Determination of monomer reactivity ratios from a single sample using multivariate analysis of the 1H NMR spectra of poly[(methyl methacrylate)-co-(benzyl methacrylate)

New Copolymers of Vinylphosphonic Acid with Hydrophilic Monomers and Their Eu3+ Complexes.

Free radical copolymerization is used for the synthesis of novel water-soluble copolymers of vinylphosphonic acid with 2-deoxy-2-methacrylamido-D-glucose or 4-acryloylmorpholine, with varied compositions and molecular masses, as well as for the synthesis of copolymers of vinylphosphonic acid with acrylamide. The obtained copolymers contain 6–97 mol.% of vinylphosphonic acid units, and their molecular masses vary from 5 × 103 to 310 × 103. The monomer reactivity ratios of vinylphosphonic acid and 2-deoxy-2-methacrylamido-D-glucose in copolymerization are determined for the first time, and their values are 0.04 and 9.02, correspondingly. It is demonstrated that the synthesized copolymers form luminescent mixed-ligand complexes with Eu3+, thenoyltrifluoroacetone, and phenanthroline. The influence of the comonomer’s nature on the intensity of the luminescence of complex solutions is revealed.

Synthesis, monomer reactivity ratios and antibacterial activity of 2-hydroxy ethyl methacrylate and 2-(Diethylamino) ethyl methacrylate copolymers

Synthesis, monomer reactivity ratios and antibacterial activity of 2-hydroxy ethyl methacrylate and 2-(Diethylamino) ethyl methacrylate copolymers

RAFT Emulsion Polymerization of Styrene Using a Poly((N,N-dimethyl acrylamide)-co-(N-isopropyl acrylamide)) mCTA: Synthesis and Thermosensitivity.

Thermoresponsive poly((N,N-dimethyl acrylamide)-co-(N-isopropyl acrylamide)) (P(DMA-co-NIPAM)) copolymers were synthesized via reversible addition−fragmentation chain transfer (RAFT) polymerization. The monomer reactivity ratios were determined by the Kelen–Tüdős method to be rNIPAM = 0.83 and rDMA = 1.10. The thermoresponsive properties of these copo-lymers with varying molecular weights were characterized by visual turbidimetry and dynamic light scattering (DLS). The copolymers showed a lower critical solution temperature (LCST) in water with a dependence on the molar fraction of DMA in the copolymer. Chaotropic and kosmotropic salt anions of the Hofmeister series, known to affect the LCST of thermoresponsive polymers, were used as additives in the aqueous copolymer solutions and their influence on the LCST was demonstrated. Further on, in order to investigate the thermoresponsive behavior of P(DMA-co-NIPAM) in a confined state, P(DMA-co-NIPAM)-b-PS diblock copolymers were prepared via polymerization induced self-assembly (PISA) through surfactant-free RAFT mediated emulsion polymerization of styrene using P(DMA-co-NIPAM) as the macromolecular chain transfer agent (mCTA) of the polymerization. As confirmed by cryogenic transmission electron microscopy (cryoTEM), this approach yielded stabilized spherical micelles in aqueous dispersions where the PS block formed the hydrophobic core and the P(DMA-co-NIPAM) block formed the hydrophilic corona of the spherical micelle. The temperature-dependent behavior of the LCST-type diblock copolymers was further studied by examining the collapse of the P(DMA-co-NIPAM) minor block of the P(DMA-co-NIPAM)-b-PS diblock copolymers as a function of temperature in aqueous solution. The nanospheres were found to be thermosensitive by changing their hydrodynamic radii almost linearly as a function of temperature between 25 °C and 45 °C. The addition of kosmotropic salt anions, as a potentially useful tuning feature of micellar assemblies, was found to increase the hydrodynamic radius of the micelles and resulted in a faster collapse of the micelle corona upon heating.