Comonomer Ratio Research Articles

Construction of Aluminum‐Porphyrin‐Based Hypercrosslinked Ionic Polymers (HIPs) by Direct Knitting Approach for CO2 Capture and In‐Situ Conversion to Cyclic Carbonates

AbstractHypercrosslinked polymers (HCPs) constructed by Friedel‐Crafts reaction have drawn increasing attention in recent decades, but their multifunctionalization remains a huge challenge. Herein, a series of aluminum‐porphyrin‐based hypercrosslinked ionic polymers have been successfully synthesized by direct knitting approach without additional electrophilic comonomers, which involves the copolymerization of neutral porphyrin monomers and ionic building. By increasing the connected nodes numbers of ionic monomers, the introduction of abundant tetraphenylmethane fragements into the porphyrin backbones endows them with high‐density ionic active sites. Accordingly, the well‐matched molar ratios of aluminum sites to nucleophilic chloride anions that work synergistically for CO2/epoxide coupling can be achieved. Al‐HIP‐2 with flexible ionic pendants and a high Al/Cl ratio allows CO2 cycloaddition to be performed at ambient conditions or with diluted CO2; while Al‐HIP‐3 with rigid ionic moieties and a relatively low Al/Cl ratio exhibits higher specific surface area and stronger CO2 capture ability. Therefore, this co‐condensation strategy provides a simple and feasible pathway for adjusting the reactivity ratios of comonomers via simple structural changes in the knitting process, thus achieving the rational construction of multifunctionalized HCPs for CO2 capture and in‐situ conversion to cyclic carbonates.

Composition Regulation by Flow Copolymerization of Methyl Methacrylate and Glycidyl Methacrylate with Free Radical Method

AbstractIt is important to match the feeding ratio of comonomers to the composition ratio in the resulting copolymers as closely as possible in industrial production, where the goal is often to produce more a homogeneous composition in copolymers. In this study, a flow copolymerization system with a conventionally initiated free radical method, together with randomly selected polymerization conditions is investigated. It is succeeded in achieving a closer match between the composition ratio and feeding ratio than previously reported in the copolymerization of styrene with methyl methacrylate and of glycidyl methacrylate with methyl methacrylate, which will widen the range of applications, by precisely controlling the mixing and heating in a flow polymerization apparatus. This is confirmed by the fact that the estimated values of reactivity ratios, r1 and r2, which are used in the reaction kinetics of copolymerization, are close to 1.

CFD modeling of the ethylene–vinyl acetate copolymerization autoclave reactor: Effects of comonomer ratio on reactor dynamics and copolymer properties

Computational fluid dynamics (CFD) modeling of an industrial ethylene–vinyl acetate autoclave copolymerization reactor was conducted to evaluate the effects of comonomer ratios on reactor dynamics and product properties, including the molecular weight distribution (MWD), and copolymer composition. To accurately predict the MWD of copolymer chains under highly nonideal mixing conditions at a reduced computational cost, the CFD-multicompartment model and probability generating function (PGF) transform were applied. The effectiveness of the developed model was validated by the satisfactorily consistent plant data and simulated results. The model revealed that an increase in the vinyl acetate (VA) content significantly decreased the temperature, promoting combinational termination and chain transfer to polymer reaction for a broad copolymer MWD. The pseudo-kinetic-based analysis showed that VA was consumed more slowly than ethylene, resulting in its lower value in the copolymer composition than that of the comonomer ratios. However, despite nonideal mixing, the copolymer composition was maintained to be uniform for the copolymers produced over the entire reactor volume. In conclusion, the proposed model can be used to understand the governing behaviors of copolymerization under nonideal mixing conditions, design commercial copolymerization reactors, and predict copolymer product qualities.

Alternating Ring-Opening Metathesis Polymerization Promoted by Ruthenium Catalysts Bearing Unsymmetrical NHC Ligands

In this paper, Grubbs- and Hoveyda–Grubbs-type olefin metathesis catalysts featuring N-cyclopentyl/N’-mesityl backbone-substituted N-heterocyclic carbene (NHC) ligands were synthesized. Their propensity to promote the alternating ring-opening metathesis copolymerization (ROMP) of norbornene (NBE) with cyclooctene (COE) or cyclopentene (CPE) was evaluated and compared to that shown by analogous N-cyclohexyl complexes. High degrees of chemoselectivity were achieved in both copolymerizations. The presence of the N-cyclopentyl substituent allowed for the achievement of up to 98% and 97% of alternating diads for NBE-COE and NBE-CPE copolymers, respectively, at low comonomer ratios. Density functional theory (DFT) studies showed that both the sterical and electronic effects of NHC ligands influence catalyst selectivity.

High-Surface-Area Metalloporphyrin-Based Porous Ionic Polymers by the Direct Condensation Strategy for Enhanced CO2 Capture and Catalytic Conversion into Cyclic Carbonates.

Metalloporphyrin-based porous organic polymers (POPs) that behave as advanced biomimetic nanoreactors have drawn continuous attention for heterogeneous CO2 catalysis in the past decades. Inspired by the double activation model of epoxides, the design and synthesis of metalloporphyrin-based porous ionic polymers (PIPs) are considered as one of the most promising approaches for converting CO2 to cyclic carbonates under cocatalyst- and solvent-free conditions. To overcome the obstacle of poor reaction activity of ionic monomers or highly irregular stacking architecture, in this paper, we have proposed and demonstrated a modular bottom-up approach for constructing a series of high-surface-area metalloporphyrin-based PIPs in high yields by the direct condensation strategy, thus boosting the close contact of multiple active sites and achieving the enhanced CO2 capture and catalytic conversion into cyclic carbonates with high turnover frequencies under mild conditions. These recyclable aluminum-porphyrin-based PIPs are featured with high surface areas, prominent CO2 adsorptive capacities, rigid porphyrin skeletons, and flexible ionic pendants, as well as the matched amounts and spatial positions of metal centers and ionic sites, in which is demonstrated to be one of the quite competitive catalysts. Therefore, this strategy of introducing ionic components into the porphyrin frameworks as flexible side chains rather than main chains and adjusting the reactivity ratios of comonomers by structure-oriented methods, provides feasible guidance for the multifunctionalization of metalloporphyrin-based POPs, thereby increasing the accessibility of multiple active sites and improving their synergistic catalytic behavior.

Blending PLA with Polyesters Based on 2,5-Furan Dicarboxylic Acid: Evaluation of Physicochemical and Nanomechanical Properties

Poly(lactic acid) (PLA) is a readily available, compostable biobased polyester with high strength and toughness, and it is excellent for 3D printing applications. Polymer blending is an economic and easy way to improve its properties, such as its slow degradation and crystallization rates and its small elongation, and thus, make it more versatile. In this work, the effects of different 2,5-furan dicarboxylic acid (FDCA)-based polyesters on the physicochemical and mechanical properties of PLA were studied. Poly(butylene furan 2,5-dicarboxylate) (PBF) and its copolymers with poly(butylene adipate) (PBAd) were synthesized in various comonomer ratios and were blended with 70 wt% PLA using melt compounding. The thermal, morphological and mechanical properties of the blends are investigated. All blends were immiscible, and the presence of the dispersed phases improved the crystallization ability of PLA. Mechanical testing revealed the plasticization of PLA after blending, and a small but measurable mass loss after burying in soil for 7 months. Reactive blending was evaluated as a compatibilizer-free method to improve miscibility, and it was found that when the thermal stability of the blend components allowed it, some transesterification reactions occurred between the PLA matrix and the FDCA-based dispersed phase after 20 min at 250 °C.

Energetic Polyoxetanes as High-Performance Binders for Energetic Composites: A Critical Review.

Energetic oxetanes, a group of energetic binders (EBs), are the focus of this review. We briefly introduce the role of binders and the difference between EBs and traditional "non-energetic" polymer binders, followed by a discussion of the synthesis and key properties of polyoxetanes. Priority is given to recent works, but a long-term perspective is provided where necessary, to illustrate the development of this field and the most relevant emerging trends. New reports on methods of obtaining oxetane polymers are presented; concerning the possibility of using a new catalyst, water: Al(C4H9)3, or the ratio of comonomers on the properties of the obtained binders. The synthesis of copolymers with the use of polymers with an oxetane ring and polyethers, polybutadiene terminated with hydroxyl groups and poly (3-difluoroaminomethyl-3-methyloxetane) is discussed. The latest developments in crosslinking reactions and crosslinking agents used are also described. The primary challenges faced by the field are identified and a perspective on the future development of polyoxetane EBs is presented.

Synthesis of reactive copolymers with peroxide functionality for cross‐linking water‐soluble polymers

AbstractA series of reactive copolymers with peroxide functionality (RCPFs) were synthesized via radical copolymerization of monomer mixtures in an organic solvent comprised of a peroxide monomer 5‐(tert‐butyl peroxy)‐5‐methylhex‐1‐en‐3‐yne, acrylamide, maleic anhydride, and butyl methacrylate. Peroxide functionality allows the RCPFs to initiate a variety of radical processes, including cross‐linking of organic polymers. Hydrophilic monomer subunits (acrylamide and maleic anhydride) within the RCPF macromolecules promote cross‐linking of water‐soluble polymers. We aimed to investigate RCPF comonomer ratio and its effects on copolymerization kinetics and composition, as well as physico‐chemical and colloidal properties. We also evaluated and characterized the kinetic parameters of the thermal decomposition of peroxide moieties in the synthesized RCPF. Findings revealed that RCPF possessed surface‐active properties and reduced surface tension at its aqueous solution–air interface. The data indicated that the decomposition process complied with the first‐order kinetics, and complex thermal analysis confirmed the presence of peroxide moieties. RCPFs' ability to cross‐link water‐soluble polymers was demonstrated on poly(acrylamide) and poly(vinyl alcohol).

Insertion of ester bonds in three terpolymerization systems

Nonbiodegradable (co)polymers with all-carbon backbone produced via radical polymerization are used in various applications. For some applications, like for example in skincare and haircare, these polymers are nonrecoverable and therefore would be preferably made biodegradable. Therefore, inserting ester bonds in the backbone via radical ring opening terpolymerization of acrylates and 2-methylene-1,3 dioxepane (MDO) could be a suitable approach to obtain biodegradable terpolymers. This report investigates the influence of batch versus semibatch process on the polymerization of three terpolymerization systems viz. (i) methacrylamide (MAAM)/n-butyl acrylate (nBA)/BMDO (5,6-Benzo-2-Methylene-1,3-Dioxepane), (ii) MAAM/nBA/MDO, and (iii) methyl methacrylate (MMA)/VAc (vinyl acetate) /MDO. We demonstrate the improvement in number of ester groups inserted and the homogeneity of insertion via semibatch polymerization processes. The process is guided via optimal monomer addition feeding profiles generated using the reactivity ratios of comonomers. Such improved insertion was demonstrated by the molecular weight distribution of fragments after alkali degradation in the investigated systems.

Biobased Copolyamides 56/66: Synthesis, Characterization and Crystallization Kinetics.

This study synthesized a series of new biobased copolyamides (co-PAs), namely PA56/PA66 with various comonomer ratios, by using in situ polycondensation. The structures, compositions, behaviors, and crystallization kinetics of the co-PAs were investigated through proton nuclear magnetic resonance (1H NMR) spectroscopy, gel permeation chromatography (GPC), Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X-ray diffraction (XRD). The influence of the composition of co-PAs on their mechanical properties and thermal stability was investigated. The co-PAs exhibited a eutectic melting point when the PA56 content was 50 mol%, with the crystallization temperature decreasing from 229 to a minimum 188 °C and the melting temperature from 253 to a minimum 218 °C. The results indicated that the tensile strength and flexural modulus first decreased and then increased as the PA66 content increased. The nonisothermal crystallization kinetics of the PA56/PA66 co-PAs were analyzed using both the Avrami equation modifications presented by Jeziorny and Mo. The results also indicated that the crystallization rate of the PA56/PA66 co-PAs was higher than that of PA56.

Determination of inline-particle sizes by turbidity measurement in high solid content emulsion polymerisations

Particle size determination in optically dense systems requires costly techniques or dilution of collected samples. Against this background, turbidimetry was investigated as a potentially robust as well as inexpensive alternative. Emulsion copolymerisations of vinyl acetate and VeoVa10® with solid contents up to 48 wt% were examined time resolved with respect to mean particle size at different temperatures, solid contents and with different co-monomer ratios and emulsifier concentrations. The mean hydrodynamic diameters were validated by dynamic light scattering (DLS). Precise number mean hydrodynamic diameters in the range from 100 to 250 nm were obtained in-line for polyvinyl acetate dispersions with deviations in particle sizes below ± 5%. In addition, the turbidity values were recorded by means of a nephelometry process probe and thus a robust, system-related calibration was created, which was subsequently able to reliably track the number mean hydrodynamic diameter inline time-resolved.

Synthesis and Characterization of Catechol-Containing Polyacrylamides with Adhesive Properties.

In this study, a row of four analogous dopamine acryl- and methacrylamide derivatives, namely N-(3,4-dihydroxyphenyethyl) acrylamide, N-(3,4-dihydroxyphenyethyl) meth acrylamide, N-phenethyl methacrylamide, N-(4-hydroxyphenethyl) methacrylamide were synthesized and characterized by 1H-NMR and 13C-NMR, followed by further solvent-based radical polymerization with N-hydroxyethyl acrylamide. All copolymers were characterized by 1H-NMR, dynamic differential calorimetry, and gel permeation chromatography. The dependency of the used comonomer ratios to the molecular mass of the corresponding copolymers has been described. The synthesis of the various polymers serves as a feasibility study and provides important data for a future biometric application in the medical field. We synthesized N-(3,4-dihydroxyphenyethyl) acrylamide copolymer up to 80 mol% by free radical polymerization without using any protecting groups. All polymers show identical perfect adhesive properties by a simple scratch test. Further, the monomers were used as a photo reactive glue formulation to test its adherence to a medical titanium surface sample by tensile shear test.

Azide Photochemistry in Acrylic Copolymers for Ultraviolet Cross-Linkable Pressure-Sensitive Adhesives: Optimization, Debonding-on-Demand, and Chemical Modification.

Pressure-sensitive adhesives (PSAs) are usually made from viscoelastic, high-molecular-weight copolymers, which are fine-tuned by adjusting the comonomer ratios, molecular weights, and cross-link densities to optimize the adhesion properties for the desired end-use. To create a lightly cross-linked network, an ultraviolet (UV) photoinitiator can be incorporated. Here, we present the first use of perfluorophenylazide chemistry to control precisely a polyacrylate network for application as a PSA. Upon UV irradiation, the highly reactive nitrene from the azide moiety reacts with nearby molecules through a C–H insertion reaction, resulting in cross-linking via covalent bonding. This approach offers three benefits: (1) a means to optimize adhesive properties without the addition of an external photoinitiator; (2) the ability to switch off the tack adhesion on demand via a high cross-linking density; and (3) a platform for additional chemical modification. A series of poly(n-butyl acrylate-co-2,3,4,5,6-pentafluorobenzyl acrylate) or poly(PFBA-co-BA) copolymers were synthesized and modified post-polymerization into the photo-reactive poly(n-butyl acrylate-co-4-azido-2,3,5,6-tetrafluorobenzyl acrylate) [azide-modified poly(PFBA-co-BA)] with various molar contents. When cast into films, the azide-modified copolymers with a high azide content achieved a very high shear resistance after UV irradiation, whereas the tack and peel adhesion decreased strongly with the increase in azide content, indicating that excessive cross-linking occurred. These materials are thus photo-switchable. However, in the low range of azide content, an optimum probe tack adhesion energy was obtained in films with a 0.3 mol % azide content, where a long stress plateau (indicating good fibrillation) with a high plateau stress was observed. An optimum peel adhesion strength was achieved with 0.5 mol % azide. Thus, the adhesion was finely controlled by the degree of cross-linking of the PSA, as determined by the azide content of the copolymer chain. Finally, as a demonstration of the versatility and advantages of the material platform, we show an azide–aldehyde–amine multicomponent modification of the azide copolymer to make a dye-functionalized film that retains its adhesive properties. This first demonstration of using azide functionality has enormous potential for functional PSA design.

Study on the thermal properties of the grafted product of maleic anhydride onto clylized natural rubber by using thermogravimetric method

This study aims to investigate the thermal properties of grafted products of maleic anhydride onto cyclized natural rubber. The grafting was carried out in the melt phase at an internal mixer of 150 oC and a rotor speed of 80 rpm. A total of 16 phr maleic anhydride was reacted with cyclized natural rubber in the present and absence of divinylbenzene comonomer with various mole ratios: 0.5, 1, and 2. The grafted products were characterized by the thermogravimetric method to investigate their thermal properties. Based on the results of the thermogravimetric analysis, it was shown that the sample increased its thermal stability. The sample decomposes at a higher temperature with the increasing mole ratio of divinylbenzene added. The grafted product with 16 phr maleic anhydride decomposed at 489.41 oC. Then, the graft product samples with the addition of 0.5, 1, and the 2-mole ratio of divinylbenzene comonomers decomposed at: 501.62 oC, 514.39 oC, and 520.82 oC, respectively.

Thermo- and pH-sensitive nanoparticles of poly (N-isopropylacrylamide-decenoic acid-1-vinylimidazole) for ultrasound switchable fluorescence imaging.

We herein report the synthesis of poly (9-decenoic acid-1-vinylimidazole-N-isopropylacrylamide) nanoparticles containing indocyanine green (ICG) in one pot and in water phase throughout the reaction. We have shown that copolymers of 9-decenoic acid and 1-vinylimidazole, or 9-decenoic acid alone, have an enhanced sensitivity to pH values between 7.4 and 6.8 and are superior to the widely used acrylic acid. We have also shown that incorporation of acidic comonomers leads to the favorable outcome of a higher fluorescence signal intensity in lower pH values, whereas the opposite is true of basic comonomers, where the fluorescence signal intensity is lower at low pH values. It was shown that to keep the pH response favorable the molar ratio of basic comonomers to acidic comonomers should roughly equal 1:4. We controlled the lower critical solution temperature (LCST) of the nanoparticles from around 30 to 38°C for different applications by adding acrylamide comonomers. Finally, the nanoparticles at varying pH values, when imaged by an ultrasound switchable fluorescence (USF) imaging system, showed pH sensitivity and thermosensitivity at physiological and tumor pH.

Thermal Property Control by Copolymerization of Trimethylene Carbonate and Its Derivative Bearing Triphenylmethyl Group

AbstractIn order to tune the thermal properites of ester‐free type poly(trimethylene carbonate) (PTMC) derivatives, the copolymers of trimethylene carbonate (TMC) and a TMC derivative bearing a triphenylmethyl group (TrTMC) were synthesized with various copolymerization ratios. The copolymers of TMC and TrTMC were obtained by varying the feeding ratio of their monomers with good yields as hexane‐isopropanol (9/1, v/v) insoluble part. The structures were confirmed by both FT‐IR and 1H NMR spectra, showing the copolymer composition was controlled in a good manner. The thermal degradation temperature at 10 % weight loss gradually increased from 198 °C to 301 °C, depending on the introduced amount of TrTMC, indicating that the thermal decomposition was based on the monomer unit structure. The glass transition temperatures of copolymers also gradually increased from −38 °C to 57 °C. These results show that the thermal properties of the ester free type TMC derivatives could be overcome by the copolymerization, and that the thermal properties could be varied by controlling the feed ratio of comonomers.

Influence of Chain Length of Gradient and Block Copoly(2-oxazoline)s on Self-Assembly and Drug Encapsulation.

Amphiphilic gradient copolymers represent a promising alternative to extensively used block copolymers due to their facile one-step synthesis by statistical copolymerization of monomers of different reactivity. Herein, an in-depth analysis is provided of micelles based on amphiphilic gradient poly(2-oxazoline)s with different chain lengths to evaluate their potential for micellar drug delivery systems and compare them to the analogous diblock copolymer micelles. Size, morphology, and stability of self-assembled nanoparticles, loading of hydrophobic drug curcumin, as well as cytotoxicities of the prepared nanoformulations are examined using copoly(2-oxazoline)s with varying chain lengths and comonomer ratios. In addition to several interesting differences between the two copolymer architecture classes, such as more compact self-assembled structures with faster exchange dynamics for the gradient copolymers, it is concluded that gradient copolymers provide stable curcumin nanoformulations with comparable drug loadings to block copolymer systems and benefit from more straightforward copolymer synthesis. The study demonstrates the potential of amphiphilic gradient copolymers as a versatile platform for the synthesis of new polymer therapeutics.

Thermo-responsive hydrogels from hyaluronic acid functionalized with poly(2-alkyl-2-oxazoline) copolymers with tuneable transition temperature

Hyaluronic acid (HA) based thermo-responsive physical hydrogels were obtained through a one-pot functionalization of HA of different molar masses (from 38 to 990 kg mol−1) with thermo-responsive poly(2-isopropyl-2-oxazoline)-co-poly(2-n-butyl-2-oxazoline) (PiPrOx-co-PnBuOx) copolymers. The cloud point (Tcp) of PiPrOx-co-PnBuOxs varied according to their monomeric composition. The functionalized HA's thermo-responsiveness was characterised through rheology and UV–vis spectrophotometry. The hydrogel transition temperature could notably be modified in a controlled way by varying the comonomers ratio in the graft, with the crossing temperature of storage modulus G′ and loss modulus G″ being found to rise by about 1 °C when increasing the iPrOx unit content within the PiPrOx-co-PnBuOx grafted copolymer by 1% for a series of modified 990 kg mol−1 HA. The thermal transition of the material from room temperature to 37 °C was found out to be almost instantaneous, which is interesting for applications in injectable systems.

Lipophilic monomer tackifying hydrogel antifouling coatings prepared by soap free emulsion polymerization and its performance

Lipophilic monomer tackifying hydrogel with good adhesion ability on organic substrates prepared in oily systems contain a large number of volatile organic compounds(VOCs). In this study, lipophilic monomer tackifying hydrogel prepolymers were fabricated in an aqueous system by soap-free emulsion polymerization to solve the above problems. The effects of reaction temperature, monomer type and comonomer ratio on soap-free emulsion polymerization were investigated. The structure of the hydrogel antifouling material was characterized by infrared spectroscopy and nuclear magnetic resonance spectroscopy. The adhesion properties of the lipophilic monomer tackifying hydrogel antifouling material on the organic substrate were investigated by a “static seawater immersion panel experiment” and “dynamic rotating seawater experiment”. The antifouling ability of the lipophilic monomer tackifying hydrogel was investigated by inhibiting the adhesion of microalgae and bovine serum albumin (BSA) and panels tests in a real marine environment. The results showed that the lipophilic monomer tackifying hydrogel antifouling material with good adhesion on an organic substrate was successfully prepared by soap-free emulsion polymerization. When the molar content of butyl acrylate was 30%, it did not fall off after 28 days of the dynamic rotating experiment. The change in water absorption caused by the acrylic acid content has a direct impact on protein adhesion. Panels in the real marine environment experiments displayed that the lipophilic monomer tackifying hydrogel had considerable inhibitory ability on biological attachment.

Stepwise Gradient Copolymers of n-Butyl Acrylate and Isobornyl Acrylate by Emulsion RAFT Copolymerizations

Gradient copolymers of n-butyl acrylate (nBA) and isobornyl acrylate (IBA) were prepared using reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization. Gradient copolymerizations were conducted using stepwise monomer addition such that the system was monomer-starved. Using the stepwise monomer addition process with a fixed comonomer ratio during the polymerization allows for pre-specified gradient compositions to be obtained. The structural properties of copolymers were confirmed via kinetic investigations and two-dimensional chromatography. 1H nuclear magnetic resonance (NMR) characterization revealed the gradient behavior of the prepared copolymers. The degree of change in monomer composition along the copolymer chain strongly affects the thermal properties of the final polymer product. Thus, gradient copolymers were examined to determine how the strength of the gradient impacts the glass-transition temperature (Tg). Comparisons were also made between the gradient copolymers and their corresponding statistical copolymers and homopolymers. Differential scanning calorimetry analysis of gradient copolymers demonstrated that such copolymers had much broader glass-transition regions compared to homopolymers and statistical copolymers. Furthermore, both the midpoint of the transition (i.e., Tg) and the breadth of the transition were found to be predeterminable through a judicious choice of the comonomer feed composition and the steepness of the comonomer feed in the subsequent monomer additions.