Homopolymerization Reactions Research Articles

Synthesis and properties of superhydrophobic monomer stearyl methacrylate-modified polyacrylate latex pressure sensitive adhesives

Hybrid surfactants of long carbon chain hydrophobic nonionic emulsifier N-390 and conventional anionic emulsifier CO-436 were utilized in this study to enable successful emulsion polymerization of super-hydrophobic monomer stearyl methacrylate (SMA) together with butyl acrylate (BA), acrylic acid (AA), and 2-hydroxyethyl acrylate (HEA). The influences of SMA on the resulting latex and film properties were thoroughly investigated. Both FTIR and 1H NMR were used to confirm the successful participation of SMA in the emulsion polymerization. The results indicated that with introduction of SMA, the roughness of the latex film increases, while the light transmission decreases. It was also found that with the addition of SMA, contact angle of the latex PSA film increased from 115.1° to 127.2°, while water absorption decreased from 5.76 to 2.89 wt%. DSC curves demonstrated that SMA has participated more in the homopolymerization reaction than in the copolymerization reaction. TGA results showed that the initial decomposition temperature (T5%) of the latex film was increased from 302.8 to 332.7 °C with the increase of SMA dosage from 0 to 20 wt%. Finally, adhesion properties results indicated that loop tack and 180° peel force of the PSA films were decreased from 11.51 to 1.88 N/25 mm and 6.36 to 3.44 N/25 mm, respectively, while shear strength was increased from 732 to 2865 min.

Grafting Starch with Acrylic Acid and Fenton's Initiator: The Selectivity Challenge.

Through the graft polymerization of acrylic monomers onto starch, materials with interesting new properties can be synthesized. Fenton's chemistry, Fe2+/H2O2, is considered to be attractive for the initiation of graft polymerization with the monomer acrylic acid since it is cheap and reacts quickly at ambient conditions and should therefore be easy to scale up. However, the selectivity of the grafting versus the homopolymerization reaction poses a challenge with this monomer and this type of initiator. In the present review paper, we investigate why data from the literature on grafting systems with other monomers and initiation systems tend to show higher graft selectivity. A scheme is presented, based on reaction engineering principles, that supports an explanation for these observed differences. It is found that more selective activation of starch is a factor, but perhaps even more important is a low monomer-to-starch ratio at the starting sites of graft reactions. Since water is the most common solvent, monomers that are less water-soluble have an advantage in this respect. Based on the proposed scheme, methods to improve the graft selectivity with Fenton's initiator and acrylic acid are evaluated. Most promising appears to be a method of gradual monomer dosage. With gelatinized cassava starch in a batch reactor, both the grafting percentage (17 => 29%) and graft selectivity (18 => 31%) could be improved. This can be considered a principal breakthrough. Still, more research and development would be needed to refine the method and to implement the idea in a continuous reactor at a larger scale.

Synthesis and study of the glycosyl-donor properties of 2-(2,2,2-trichloroethoxy)-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-galactopyrano)-[2,1-d]-2-oxazoline

A synthesis of 2-(2,2,2-trichloroethoxy)-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-d-galactopyrano)-[2,1-d]-2-oxazoline – a previously unknown 2-alkoxy glyco-[2,1-d]-2-oxazoline derivative with d-galacto configuration was carried out. Glycosylating activity of the obtained galactooxazoline has been studied and it has been shown that in the presence of a weak protic acid, such as sym-collidinium triflate, this substance exhibits properties of a reactive and 1,2-trans-stereoselective glycosyl donor. The homopolymerization reaction of oxazoline derivatives of sugars has been found to proceed under the same conditions, leading to the formation of pseudo-oligosaccharide products. It has been found that this undesirable side reaction could be suppressed by changing the acid catalyst concentration, resulting in the development of efficient methods for the synthesis of glycoside and oligosaccharide derivatives of β-d-galactosamine using the synthesized 2-(2,2,2-trichloroethoxy)-2-oxazoline glycosyl donor under very mild conditions.

Influence of the Ethanol Content of Adduct on the Comonomer Incorporation of Related Ziegler-Natta Catalysts in Propylene (Co)polymerizations.

The aim of this work is to investigate the influence of the ethanol content of adducts on the catalytic behavior of related Ziegler-Natta (ZN) catalysts in propylene homo- and copolymerizations (with 1-hexene comonomer) in terms of activity, isotacticity, H2 response, and comonomer incorporation. For this purpose, three MgCl2.nEtOH adducts with n values of 0.7, 1.2, and 2.8 were synthesized and used in the synthesis of related ZN catalysts. The catalysts were thoroughly characterized using XRD, BET, SEM, EDX, N2 adsorption-desorption, and DFT techniques. Additionally, the microstructure of the synthesized (co)polymers was distinguished via DSC, SSA, and TREF techniques. Their activity was found to enhance with the adduct's ethanol content in both homo- and copolymerization experiments, and the increase was more pronounced in homopolymerization reactions in the absence of H2. Furthermore, the catalyst with the highest ethanol content provided a copolymer with a lower isotacticity index, a shorter meso sequence length, and a more uniform distribution of comonomer within the chains. These results were attributed to the higher total surface area and Ti content of the corresponding catalyst, as well as its lower average pore diameter, a larger proportion of large pores compared to the other two catalysts, and its spherical open bud morphology. It affirms the importance of catalyst/support ethanol-content control during the preparation process. Then, molecular simulation was employed to shed light on the iso-specificity of the polypropylene produced via synthesized catalysts.

Improving Glass Transition Temperature and Toughness of Epoxy Adhesives by a Complex Room-Temperature Curing System by Changing the Stoichiometry

The glass transition temperature (Tg) of room-temperature curing epoxy adhesives is limited by the temperature used during curing. It is already known that the excess of epoxy groups can undergo a homopolymerization reaction initiated by tertiary amines at elevated temperatures, resulting in an increase in Tg. However, there is no evidence of this reaction occurring at room temperature. In the present work, the influence of formulation stoichiometry on Tg and mechanical properties was investigated. Dynamomechanical, rheological and mechanical properties of epoxy adhesives were determined by DSC, DMA, rheometer and tensile and shear strength testing. It has been probed that an excess of epoxy resin combined with a complex curing system composed of a primary amine, a polymercaptan and a tertiary amine leads to an increase in Tg up to 70 °C due to the homopolymerization reaction that takes place at room temperature. However, as the excess of epoxy resin is increased, gel time becomes slower. Regarding mechanical properties, it has been proven that an excess of epoxy resin provides a tighter and tougher material but maintains flexibility of the stoichiometric formulation, which is meant to enhance the resistance to impact-type forces, thermal shock and thermal cycling.

SYNTHESIS AND RADICAL POLYMERIZATION OF BENZAMIDMETACRYLATE

The data on the synthesis of the new monomer benzamidmetacrylate are presented in the article. Its composition and structure were established by physical and chemical methods of research. The regularities of radical homopolymerization reactions in mass and in benzene solution were studied with the aim of creating a new biocidal polymeric material for medical preparations. It is shown that polymerization under these conditions proceeds through the vinyl bond, without an induction period, at a constant initial rate without the formation of by-products, a monotonic increase in conversion up to 92% with the formation of a soluble polymer is observed. The composition and structure of the obtained polymer were established by elemental and spectral analyses. It showed that the polymer was characterized by a low toxicity at a significant biocidal activity towards E.coli and St.Aureus and that this polymer can be used in various fields, in particular as a biocidal preparation, a carrier of dosage forms in medicine. In addition, this polymer also exhibites optical translucency and can be used in optics.

Palladium(II) Complexes with the 4,5‐Bis(diphenylphosphino)acenaphthene Ligand and Their Reactivity with Ethylene

AbstractThe last two decades have witnessed the development of homogeneous catalysts for ethylene homo‐ and co‐polymerization reactions based on late transition metals. When Pd(II) is the metal of choice, the best ligand‐metal combination deals with either bidentate nitrogen‐donor molecules or phosphinobenzene sulfonate derivatives. In this contribution we have investigated the coordination chemistry to Pd(II) of a bidentate phosphorus ligand, namely 4,5‐bis(diphenylphosphino)acenaphthene (1). Starting from the neutral complex, [Pd(1)(CH3)Cl], we obtained the cationic derivatives [Pd(1)(CH3)(L)][SbF6], with L being either CH3CN or 3,5‐lutidine. Using in situ NMR spectroscopy we investigated the reaction of [Pd(1)(CH3)(NCCH3)][SbF6] with ethylene, at room temperature, and ambient ethylene pressure. We discovered that [Pd(1)(CH3)(NCCH3)][SbF6] acts as a catalyst for butenes and hexenes synthesis with the relevant Pd‐ethyl intermediate as the catalyst resting state. At the same time the color of the solution turned from pale yellow to light red due to the formation of the dinuclear species [Pd(μ‐η2−C6H5)PPh)−PPh2]2[SbF6]2. Both the neutral Pd(II) complex, activated in situ by NaSbF6, and the monocationic acetonitrile derivative were tested in the ethylene homopolymerization reaction at high pressure, leading to low molecular weight, branched, polyethylene.

SYNTHESIS AND STUDY OF COPOLYMERS OF METHYL METHACRYLATE WİTH OLIGOPROPYLENE MACROMONOMERS

The reaction of radical copolymerization of oligopropylene macromonomer (M1) with methyl methacrylate (M2) has been carried out, the regularities of the reaction and the properties of the obtained products have been studied. It has been found that the values of the relative activity of these monomers are r1=0.02 and r2=12.2, respectively. The fact that the value of the copolymerization constant of the oligopropylene macromonomer is close to zero indicates that it is not prone to homopolymerization reactions and only undergoes copolymerization reactions. The dependence of some properties of the synthesized copolymer on their composition has been studied and it has been shown that with an increase in the amount of the fragment formed from the oligopropylene macromonomer, the softening temperature and intrinsic viscosity values of the copolymers decrease, and, accordingly, a sharp decrease in the average molecular weight is observed. This is due to the passivity of the oligopropylene macromonomer in copolymerization reactions and the high probability of a chain transfer reaction through the oligopropylene macromonomer.

Alkene polymerization reactions with catalysts based on acetylacetonate complexes of vanadium and titanium: effect of cocatalyst

AbstractAlkene polymerization reactions were studied with three catalyst systems containing complexes of vanadium and titanium with the acetylacetonate ligand (V(acac)3, VO(acac)2, Ti(acac)2Cl2) and a binary activator, a combination of Al(C2H5)2Cl and Mg(C4H9)2 at an [Al]:[Mg] molar ratio of ca 3. All three catalysts are highly active in ethylene homopolymerization reactions. They copolymerize ethylene and 1‐hexene to random, compositionally uniform products with 1‐hexene content of up to 20–25%. The Ti(acac)2Cl2–Al(C2H5)2Cl/Mg(C4H9)2 combination is also an effective catalyst for propylene polymerization to an essentially atactic product. Gel permeation chromatography analysis showed that all the studied M(acac)n–Al(C2H5)2Cl/Mg(C4H9)2 catalysts contain several types of active centers which differ in the average molecular weight of polymer material they produce. © 2021 Society of Industrial Chemistry.

Ene/Diene Copolymerization Catalyzed by Cationic Sc and Gd d0 Metal Complexes: Speciation, Ion Pairing, and Selectivity from a Computational Perspective

A computational mechanistic study of the butadiene homopolymerization reaction performed with scandium and gadolinium catalysts [(2-Me-Ind)2(N(TMS)2)]M (M = Sc, Gd) in presence of [Ph3C][B(C6F5)4] ...

PHYSICO-CHEMICAL POLYMER AND HYDROGEL ON THE BASIS OF 1-CHLORO-3- PIPERIDINE-2-PROPYLACRYLATE

The radical polymerization of a new monomer with a piper dine cycle in the presence of a nitrogen-containing initiator in the environment of organic solvents was investigated. The influence on the polymerization process of such factors as the nature of the solvent, temperature, monomer and initiator concentration is studied. The main kinetic and energy parameters of the homopolymerization reaction are determined. The found values of the reaction orders for the monomer and initiators are 1.01 and 0.53, respectively, and the process activation energy is 56.7 kJ / mol. A synthesized cross-linked high molecular compound based on 1-chloro-3-piperidino-2-propylacrylate. The physicochemical properties of the obtained compound were studied, the rate of swelling in water and other media, resistance to degradation, and mechanical strength were determined. The synthesis of a polymer gel based on the ester of 1-chloro-3-piperidino-2-propyl acrylate is given in the article. Optimal conditions for obtaining the gel were chosen. The physical and chemical properties of solutions of the obtained hydrogels, including the kinetics of swelling of gels in aqueous solutions, are studied.

Modeling and Observer-Based Monitoring of RAFT Homopolymerization Reactions

Reversible addition–fragmentation chain–transfer (RAFT) polymerization of methyl methacrylate (MMA) is modeled and monitored using a multi-rate multi-delay observer in this work. First, to fit the RAFT reaction rate coefficients and the initiator efficiency in the model, in situ 1 H nuclear magnetic resonance (NMR) experimental data from small-scale (<2 mL) NMR tube reactions is obtained and a least squares optimization is performed. 1 H NMR and size exclusion chromatography (SEC) experimental data from large-scale (>400 mL) reflux reactions is then used to validate the fitted model. The fitted model accurately predicts the polymer properties of the large-scale reactions with slight discordance at late reaction times. Based on the fitted model, a multi-rate multi-delay observer coupled with an inter-sample predictor and dead time compensator is designed, to account for the asynchronous multi-rate measurements with non-constant delays. The multi-rate multi-delay observer shows perfect convergence after a few sampling times when tested against the fitted model, and is in fair agreement with the real data at late reaction times when implemented based on the experimental measurements.

Practical procedure for a theoretical investigation of thermodynamics and kinetics aspects of different-scale radical reactions from addition and cyclization to cyclocopolymerization involving maleic anhydride and divinyl ether

Quantum chemical techniques reasonable in practical simulation of carbon-centered radical reactions were evaluated scaling up from addition and cyclization of small radicals to growing chains in homo-, cross- and cyclo-polymerization. The methods preselected via “cost – deviation from experiment” criteria were explored relative to growing molecular systems of radical cyclocopolymerization between divinyl ether and maleic anhydride: alternating cross-propagation with cyclization and side homopolymerization reactions. The following methods were found to be optimal for estimation of activation barriers and thermodynamics parameters: DFT M06-2X with 6-311+G(d) and 6-311+G (2df,p) basis sets or ONIOM M06-2X/6-311+G(d):B3LYP/6-31G(d) – for more complex systems. Spin-restricted open shell calculations by ROMP2/6-311+G (3df, 2p) have shown unfeasible increase in computational costs retaining similar accuracy. The optimal techniques facilitated new mechanistic insights into regulating the polymerization including kinetic-thermodynamic control factors for regulation of furan-/pyran-related isomerism within the chain that is essential for tailoring functionality of the derivatives. The approach builds methodology basis for research of similar macromolecular systems including alike polymeric platforms for preparations of broad biomedical applications.

POSS-containing hybrid nanomaterials based on thiol-epoxy click reaction

Organic-inorganic nanocomposites were designed by combining a commercial epoxy resin (diglycidyl ether of bisphenol A - DER) and a multi-thiol crosslinking agent with a “clickable” polyhedral oligomeric silsesquioxane (POSS) compound. 1-methylimidazole was employed as a catalyst to yield highly efficient thiol-Michael addition reaction materials. The equivalent ratio between epoxy: thiol was maintained 1:1 in all the formulations and therefore the homopolymerization reaction of epoxy resin is unlikely to occur. The synergistic effect of the thiol compound and mono-functionalized POSS bearing one epoxy/thiol reactive group on the curing process was investigated in detail. We assume that the mechanistic pathway of the thiol-epoxy click-reaction increases in complexity due to the introduction of reactive POSS in the system. The incorporation of mono-epoxy or mono-thiol POSS in the thiol–epoxy organic host leads to distinct thermo-mechanical behavior of the crosslinked networks due to the fact that the POSS compound will chemically interact in the click reaction.

Novel hydrogels based on a high‐molar‐mass water‐soluble dimethacrylate monomer

AbstractThis report describes the preparation and swelling behaviour of novel hydrogels based on a water‐soluble dimethacrylate monomer (EBisEMA), which is characterized by a relatively high molar mass (Mn ∼ 1700 g mol−1) and contains a high proportion of aliphatic ether bonds in its structure. This feature results in moderately crosslinked and flexible polymer networks. Significant differences were observed in degree of swelling, depending on the synthesis method employed to obtain the hydrogels. The equilibrium water sorption of EBisEMA photopolymerized in bulk was 68 wt% while that of EBisEMA photopolymerized in aqueous solution (0.5 g mL−1) was 104 wt%. Thiol–methacrylate hydrogels were prepared by visible light photopolymerization of EBisEMA with a tetrafunctional thiol (PETMP) at various EBisEMA‐to‐PETMP molar ratios. These hydrogels contained unreacted thiol groups because of a faster homopolymerization reaction of EBisEMA. Hydrogels were also prepared in bulk by propylamine‐catalysed Michael addition reaction. No significant differences in swelling were observed between EBisEMA homopolymer and photocured EBisEMA–PETMP copolymer. Conversely, a marked increase in water uptake (110 wt%) was observed in the EBisEMA–PETMP hydrogels prepared by the Michael addition reaction catalysed by propylamine. These trends are explained in terms of a balance between the mass fraction of hydrophilic groups and the crosslinking density of the network. EBisEMA–PETMP hydrogels formulated with thiol in excess showed a noticeable tendency to adhere to diverse substrates, including paper, metals, glass and skin. This feature makes them especially attractive in applications for which adhesion is particularly critical such as dermatological patches. © 2018 Society of Chemical Industry

Novel high reactive bifunctional five- and six-membered bicyclic dicarbonate - synthesis and characterisation.

Five- and six-membered bicyclic carbonates are valuable raw materials for the synthesis of environmentally friendly polymers, such as polycarbonates or non-isocyanate poly(hydroxyurethane)s. However, bicyclic diglycerol dicarbonates bearing five-membered and six-membered rings have been never reported before. In this work, for the first time, we report a simple procedure for the synthesis of this monomer from commercially available diglycerol. The product was characterised by 1H NMR, 13C NMR, FTIR spectroscopy and X-ray diffraction measurements. Next, the reactivity of the obtained bicyclic carbonate was investigated. The obtained diglycerol dicarbonate was used as a monomer for polycarbonate and non-isocyanate poly(hydroxyurethane) based on putrescine. In the homopolymerisation reaction the opening of the six-membered carbonate ring was observed, while in the polycondensation with diamine both carbonate rings open nonselectively.

Sequential dual curing by selective Michael addition and free radical polymerization of acetoacetate-acrylate-methacrylate mixtures

A new family of poly(keto ester)-poly(methacrylate) thermosets based on off-stoichiometric acetoacetate-acrylate/methacrylate formulations has been prepared and characterized. The first stage of curing is a self-limiting click Michael addition between acetoacetate and acrylate groups at room temperature and the second stage is a methacrylate radical photopolymerization.An analysis of the reaction kinetics confirmed that acetoacetate reacts selectively with acrylates, leaving methacrylates completely unreacted after the first curing stage. It was found that acrylate-rich mixtures achieve complete conversion at the end of both curing stages. In methacrylate-rich formulations the dilution effect of this monomer leads to a slow curing rate and a certain amount of unreacted acrylates in the first curing stage, which react completely after irradiation in the second curing stage.The prepared materials are gelled after acetoacetate/acrylate Michael addition and show a wide range of properties at both curing stages that can be tailored by changing the relative contribution of the Michael and radical vinyl homopolymerization reactions. The latency of the formulations at the beginning of the second stage can be regulated as desired by irradiation.

Interfacial kinetics in a model emulsion polymerisation system using microelectrochemical measurements at expanding droplets (MEMED) and time lapse microscopy

Physicochemical processes that take place at the oil-water interface of an epoxy-amine emulsion polymerisation system influence the properties and structural morphology of the polymeric microparticles formed. Investigating these processes, such as the transport of monomers across the liquid/liquid interface brings new understanding which can be used to tune polymeric morphology. Two different approaches are used to provide new insights on these processes. Microelectrochemical measurements at expanding droplets (MEMED) is used to measure the transfer of amine from an organic phase comprised of epoxide and amine into an aqueous receptor phase. The rate of amine transfer across the liquid/liquid interface is characterised using MEMED and finite element method modelling and kinetic values are reported. Time lapse microscopy of epoxide droplets held in deionised water or an aqueous amine solution heated to different temperatures is further used to characterise epoxide dissolution into the aqueous phase. Mass-transport of epoxide into the aqueous phase is shown to be temperature-dependent. Epoxide homopolymerisation at the droplet-water interface is found to influence the rate of epoxide droplet dissolution. The rate of the epoxy-amine cure reaction is shown to be faster than the rate of the epoxide homopolymerisation reaction. The combination of methods used here is not limited to emulsion polymerisation and should find application in a myriad of processes at liquid/liquid interfaces.

Aluminum complex initiated copolymerization of lactones and DL‐lactide to form crystalline gradient block copolymers containing stereoblock lactyl chains

ABSTRACTThe homopolymerization reactions of several lactones, as well as the copolymerization reactions of DL‐lactide with these lactones were investigated using tridentate Schiff base aluminum complexes as the initiators. ε‐Caprolactone and δ‐valerolactone polymerized efficiently at room temperature to afford polyesters, whereas β‐butyrolactone only gave the corresponding oligomer. The copolymerization reactions of DL‐lactide with caprolactone and valerolactone yielded gradient block copolymers where the lactyl blocks formed crystalline stereoblocks as a consequence of the stereoselective polymerization of DL‐lactide in the presence of the aluminum complexes. These polymerization processes were highly controlled in nature, and block copolymerization where caprolactone copolymerized using poly(DL‐lactide)‐Al complex proceeded. The obtained gradient copolymer containing stereoblock lactyl blocks and caproyl blocks were analyzed using WAXD analysis to uncover existence of the crystalline stereoblock lactyl blocks in the copolymer. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.2016,54, 2536–2544

Preparation of PLLA/PMMA and PLLA/PS binary blend nanoparticles by incorporation of PLLA in methyl methacrylate or styrene miniemulsion homopolymerization

Miniemulsion homopolymerization reactions of methyl methacrylate (MMA) and styrene (STY) using poly(L-lactide) as co-stabilizer were carried out in order to prepare poly(L-lactide)/poly(methyl methacrylate) (PLLA/PMMA) and poly(L-lactide)/polystyrene (PLLA/PS) binary blend nanoparticles. The effect of PLLA concentration on methyl methacrylate (MMA) and styrene (STY) homopolymerization reactions was evaluated. It was found that the incorporation of PLLA resulted on acceleration of MMA and STY homopolymerization reactions and led to a molar mass increase of up to 70% for PS in PLLA/PS blend nanoparticles in relation to those prepared without PLLA, which can be attributed to an increase of reaction loci viscosity (gel effect). PLLA also acted as an efficient co-stabilizer, since it was able to retard diffusional degradation of droplets when no other kind of co-stabilizer was used. Two isolated Tgs were found in both PLLA/PMMA and PLLA/PS blend nanoparticles which can be associated to blend immiscibility. TEM images corroborate these results, suggesting that immiscible PLLA/PMMA and PLLA/PS blend nanoparticles could be formed with two segregated phases and core-shell morphology.