Final Polymer Research Articles

Enzymatic Poly(octamethylene suberate) Synthesis by a Two-Step Polymerization Method Based on the New Greener Polymer-5B Technology

Here, we report a new two-step enzymatic polymerization strategy for the synthesis of poly(octamethylene suberate) (POS) using an immobilized Pseudozyma antarctica lipase B (IMM-PBLI). The strategy overcomes the lack of enzymatic POS synthesis in solvent-free systems and increases the final polymer molecular weight. In the first step, the direct polycondensation of suberic acid and 1,8-octanediol was catalyzed by IMM-PBLI at 45 °C, leading to the production of prepolymers with molecular weights (MWs) of 2800, 3400, and 4900 g mol−1 after 8 h in miniemulsion, water, and an organic solvent (cyclohexane: tetrahydrofuran 5:1 v/v), respectively. In the second polymerization step, wet prepolymers were incubated at 60 or 80 °C, at atmospheric pressure, in the presence of IMM-PBLI, and without stirring. The final POS polymers showed a significant increase in MW to 5000, 5800, and 19,800 g mol−1 (previously synthesized in miniemulsion, water, or organic solvent, respectively). FTIR analysis of the final polymers confirmed the successful POS synthesis and a high degree of monomer conversion. This innovative two-step polymerization strategy opens up a new opportunity for implementing greener and more environmentally friendly processes for synthesizing biodegradable polyesters.

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.

A combined experimental and molecular simulation study on stress generation phenomena during the Ziegler-Natta polyethylene catalyst fragmentation process.

The morphology of particles obtained under different pre-polymerization conditions has been connected to the stress generation mechanism at the polymer/catalyst interface. A combination of experimental characterization techniques and atomistic molecular dynamics simulations allowed a systematic investigation of experimental conditions leading to a certain particle morphology, and hence to a final polymer with specific features. Atomistic models of nascent polymer phases in contact with magnesium dichloride surfaces have been developed and validated. Using these detailed models, in the framework of McKenna's hypothesis, the pressure increase due to the polymerization reaction has been calculated under different conditions and is in good agreement with experimental scenarios. This molecular scale knowledge and the proposed investigation strategy would allow the pre-polymerization conditions to be better defined and the properties of the nascent polymer to be tuned, ensuring proper operability along the whole polymer production process.

Novel hydrolytically stable Lewis acidic ionic liquid catalyst system for polybutylene succinate (PBS) synthesis

A new Lewis acidic ionic liquid catalyst system with improved catalytic activity and hydrolytic stability has been developed for the synthesis of poly(butylene succinate). Improved thermal stability of the final polymer is an added advantage of our new catalyst system.

Additive Effect on the Structure of PEDOT:PSS Dispersions and Its Correlation with the Structure and Morphology of Thin Films.

We reported on the interaction between poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and high-boiling-point additives in PEDOT:PSS aqueous dispersions and in the final polymer films with the aim of stablishing correlations between the structure of both inks and solid thin films. By Small-Angle X-ray Scattering (SAXS) using synchrotron radiation, it was found that the structural changes of dispersions of PEDOT:PSS with high-boiling-point additives can be explained as a two-step mechanism depending on the additive concentration. A compaction of PEDOT:PSS grains was observed at low concentrations while a swelling of the grains together with a phase segregation between PEDOT and PSS segments was evidenced at larger concentrations. Thin films’ morphology and structure were investigated by atomic force microscopy (AFM) and synchrotron Grazing Incidence Wide-Angle X-ray Scattering (GIWAXS) respectively. Our two-step model provides an explanation for the small and sharp domains of PEDOT:PSS thin films observed for low-additive concentrations (first step) and larger domains and roughness found for higher-additive concentrations (second step). A reduction of the ratio of PSS in PEDOT:PSS thin films upon the presence of additives was also observed. This can be related to a thinning of the PSS shells of PEDOT:PSS grains in the dispersion. The results discussed in this work provide the basis for a controlled tuning of PEDOT:PSS thin films structure and the subsequent electrical properties.

Controlled block-polymerization of styrene, divinylbenzene and ethylene oxide. Intermolecular cross-linking towards well-defined miktoarm copolymer stars

• Synthesis of well-defined miktoarm copolymer stars. • Control over the molecular weight and composition for both arm species. • Controlled polymerization of poly(divinylbenzene). • Intermolecular cross-linking of linear triblock terpolymers. A novel approach for the synthesis of miktoarm copolymer stars with divinylbenzene cross-linked core, via anionic polymerization is reported. This synthetic route gives access to polymers, characterized by low dispersity values and improved structural homogeneity for both arm species. Specifically, miktoarm copolymer stars of A n B n type, with cross-linked divinylbenzene (DVB) core and arms of polystyrene (PS) and poly(ethylene oxide) (PEO), are synthesized via anionic polymerization and sequential monomer addition, employing high vacuum techniques. Analytically, the first step involves the synthesis of a triblock terpolymer PS- b -PDVB- b -PEO. Then, in the presence of a free radical initiator the pending vinyl groups of the middle DVB block cross-link intermolecularly, leading to the final miktoarm copolymer star. The novelty of the proposed synthetic route, lies in the potassium alkoxide co -initiator, which is responsible for the controlled polymerization of both DVB and EO in one pot, without the need for end group modification between the two steps. Concerning the final polymer, there are numerous benefits advancing from this synthetic protocol, such as the control of the molecular characteristics of both arms, as well as the easily confirmed structural integrity of the precursor triblock which is inherited to the resulting miktoarm star. For comparison reasons, another batch of (PS)(PEO) miktoarm copolymers was synthesized, following the “in-out” synthetic route. For this reason, styrene was polymerized using s -BuLi, which is used as macroinitiator for the polymerization/cross-linking of DVB, resulting PS star with DVB cross-linked core. With the addition of EO, in the presence of p4 t -Bu phosphazene base, PEO arms are polymerized, initiating from the core’s active cites outwards.

Tetramethacrylic benzylidene cyclopentanone dye for one- and two-photon photopolymerization

The crystalline one-component methacrylate containing photoinitiator 4MetBAC was synthesized and characterized by 1H NMR, 13C NMR, IR-, UV–Vis spectrum, and X-Ray analysis. The one- and two-photon absorption, photoluminescence, and electrochemical properties of 4MetBAC in solution were investigated. The polymerization of PETA was induced directly by 4MetBAC (2.5–11.5 mM) under irradiation with LED@380 (1PP) or focused beam of femtosecond laser with wavelength 780 nm (2PP). The polymer nanostructures with intricate architecture («sleepers-rails»-, «cell scaffold»- and cylindrical spiral structures) were fabricated by the DLW method. The polymerization threshold of the composition based on 4Met-BAC (11.5 mM) was 0.9 mW at the recording speed of 170 μm/s. The smallest stable structures with the linear fragment sizes of 72 ± 5 nm (less than λ/10) have been obtained by nanolithography. Due to the polymerizable groups, 4Met-BAC has the ability to link into the polymer networks. Experiments with human dermal fibroblasts and cells of the HEK 293 line have been demonstrated that the final polymers prepared by both one- and two-photon photopolymerization (cell scaffold) are biosafety. Hence we believe that the PETA composition based on one-component methacrylate-containing photoinitiator 4Met-BAC opens up wide capabilities for creating three-dimensional topological structures with high submicron resolution by the DLW method for optoelectronic and biological applications.

Microwave-assisted synthesis of lanthanide coordination polymers with 2-bromobenzoic acid as ligand from hexa-lanthanide molecular precursors

Microwave-assisted reactions, between 2-bromobenzoic acid (2-bbH) and hexa-lanthanide molecular precursors of general chemical formula Ln6(µ6-O)(µ3-OH)8(NO3)6(H2O)12·2NO3·2H2O [Ln6], lead to iso-structural 1D coordination polymers of general chemical formula [Ln(2-bb)3]∞ with Ln = Eu, Tb or Dy. These compounds crystallize in the monoclinic system, space group P21/c (n°14), with the following cell parameters (for the Dy-derivative): a = 12.3809(10) Å, b = 21.8653(16) Å, c = 7.9119(7) Å, β = 98.709(3)°, V = 2117.2(3) Å3 and Z = 4. The influence of the hexa-nuclear precursors over the final coordination polymer is demonstrated. Indeed, while the hexa-nuclear complexes collapse during the synthetic process their progressive destruction affords a unique 1D coordination polymer that cannot be readily obtained otherwise. Additionally, some iso-structural hetero-lanthanide derivatives with general chemical formulas [EuxTb1-x(2-bb)3]∞ and [YxTb1-x(2-bb)3]∞ with 0 ≤ x ≤ 1 have been prepared from the corresponding hexa-nuclear complexes [Eu6xTb6-6x] and [Y6xTb6-6x], respectively. Luminescent properties have been recorded and colorimetric coordinates have been calculated for all the compounds. These measurements indicate that the molecular chains host strong intermetallic energy transfers.

Study of UV-initiated polymerization and UV crosslinking of acrylic monomers mixture for the production of solvent-free pressure-sensitive adhesive films

UV-polymerizable and UV-crosslinkable pressure-sensitive adhesive acrylic compositions are widely applied for high-quality carrier-free films, one-sided or double-sided self-adhesive tapes. Comprehensive studies of the properties of novel acrylic PSAs for carrier-free films or adhesive tapes were carried out. Solvent-free acrylic pressure-sensitive adhesive layers were UV-crosslinked using various photoreactive crosslinking agents. Polymer content during UV-polymerization, prepolymers viscosity, temperature changes of prepolymer during UV-initiated polymerization process were investigated. The chemical structure of prepolymer and polymerized acrylic film were examined using FTIR spectroscopy. Prepolymer mixtures were transferred on the transparent carriers to form 1 mm thick polymer films, and then UV-crosslinked after the addition of the selected acrylic crosslinker. Final adhesive films were then tested to evaluate their functional properties as the tack, peel adhesion, and shear strength at 20 °C and 70 °C. From the results reveal that both concentrations of acrylic acid in the prepolymer, and cross-linking agent in the final polymer layer, have a significant influence on the functional properties of the produced PSA films.

Molecular simulation of a reverse osmosis polyamide membrane layer. In silico synthesis using different reactant concentration ratios

We use molecular dynamics simulations at the atomistic level to build a model of aromatic polyamide polymer used in reverse osmosis membranes, from a mixture of m-phenylene diamine (MPD) and trimesoyl chloride monomers (TMC). Our purpose is to use different MPD to TMC ratios to reproduce the compositional depth-dependence observed experimentally during interfacial polymerization. MPD to TMC ratios in the range 1:4 to 5:1 have been employed. Reproducibility of the polymerization algorithm is thoroughly studied through the building of several samples under identical conditions. We notice that simulation time of a few microseconds are necessary in order to reach equilibration. We show that the initial monomer ratio has a strong influence onto the final polymer composition and different chemical structures have been created. Large differences are seen concerning cross-linking degree and remaining un-reacted groups. Comparison with available experimental data show that samples built using intermediate values of the MDP to TMC ratio closely resemble aromatic polyamide membranes. We conclude that the simulated samples created under different local concentrations can describe properly the chemical heterogeneities observed experimentally in reverse osmosis membranes.

Effects of polymerization parameters on the slow crack growth resistance and rheological properties of bimodal polyethylene resins

AbstractIn this paper, using a comprehensive study, we have investigated the effect of various polymerization parameters during the synthesis of bimodal polyethylene resins on their rheological and mechanical properties. Bimodal polyethylene resins were synthesized in two subsequent stages in a lab‐scale reactor by manipulating a set of parameters such as C2/H2 ratios in the first and second stages, the split value, and the comonomer type. The results showed that the comonomer type and C2/H2 ratio of the second stage of the polymerization are the most critical parameters that control the final resins' slow crack growth resistance properties. On the other hand, the shear‐thinning behavior of the resins is mainly controlled by the first‐stage polymers. Although the C2/H2 ratio of the first stage results in a moderate effect on the rheological properties of the final resins, its split value governs the flow characteristics of the final molten polymers under high shear rates.

A new acrylated monomer from macaw vegetable oil that polymerizes without external photoinitiators

The photopolymerization process has been widely studied due to its use in painting/coating, dentistry, creating photoresist materials and more recently in 3D printing. Therefore, new monomers have been synthesized to be used in this growing area. Here, a new Brazilian biomass derived, renewable monomer from macaw vegetable oil is presented. This monomer can self-polymerize without photoinitiation under UV light, reaching a monomer conversion of 75% and a conversion of 88% when ethyl 4-(dimethylamino)benzoate is present as a coinitiator. Furthermore, the final polymer has an orange color under visible light and exhibits fluorescence (a blue color) under UV radiation. Monomers and polymers formed from macaw (macaúba) vegetable oil are thermally stable up to 220 °C, as evidenced by thermogravimetry (TG). The polymers formed also exhibited a glass transition temperature of 2.6 °C, as observed in differential scanning calorimetry (DSC) curves and dynamic-mechanical analysis (DMA). This new monomer presents an alternative monomer to be used in 3D printing, in a similar manner to other vegetable oils such as soybean and linseed.

Dynamic Nanoconfinement Enabled Highly Stretchable and Supratough Polymeric Materials with Desirable Healability and Biocompatibility.

Lightweight polymeric materials are highly attractive platforms for many potential industrial applications in aerospace, soft robots, and biological engineering fields. For these real-world applications, it is vital for them to exhibit a desirable combination of great toughness, large ductility, and high strength together with desired healability and biocompatibility. However, existing material design strategies usually fail to achieve such a performance portfolio owing to their different and even mutually exclusive governing mechanisms. To overcome these hurdles, herein, for the first time a dynamic hydrogen-bonded nanoconfinement concept is proposed, and the design of highly stretchable and supratough biocompatible poly(vinyl alcohol) (PVA) with well-dispersed dynamic nanoconfinement phases induced by hydrogen-bond (H-bond) crosslinking is demonstrated. Because of H-bond crosslinking and dynamic nanoconfinement, the as-prepared PVA nanocomposite film exhibits a world-record toughness of 425± 31MJ m-3 in combination with a tensile strength of 98MPa and a large break strain of 550%, representing the best of its kind and even outperforming most natural and artificial materials. In addition, the final polymer exhibits a good self-healing ability and biocompatibility. This work affords new opportunities for creating mechanically robust, healable, and biocompatible polymeric materials, which hold great promise for applications, such as soft robots and artificial ligaments.

Separation of volatile compounds from polymers by physisorption

• A proof-of-principle for polymer purification by physisorption (3P) is reported. • Different model (co)polymers were succesfully isolated by the 3P method. • The chemical and macromolecular properties of the final polymers were unaltered. • The adsorbed polymers could be recovered and used for further experimentations. • The 3P method is cost-effective for separating volatile compounds from polymers. After synthesis, specialty polymers can be difficult to purify from residual volatile monomers and solvents in a precise and reproducible manner using current standard separation techniques, which also generate large amounts of waste. Herein, we report a proof-of-principle study of a cost-effective and versatile method for separating residual volatile compounds from synthetic polymers via physisorption ( i.e. , polymer purification by physisorption (3P)). Model polymers were used to evaluate the capabilities and advantages of the 3P method over standard purification techniques regarding separation of volatile compounds, process solvent to polymer yield, and final properties of the resulting polymers. Compared to dialysis and precipitation, the 3P method could separate up to 99% of the residual monomer from a polymerization reaction using a significantly lower fraction of solvent. Unlike the benchmark methods, the molar mass and dispersity of polymers purified by the 3P process remain practically unaffected; polymers were quantitatively recovered for subsequent applications ( e.g. , precursors for block copolymer synthesis or characterization purposes). The 3P method represents a straightforward technique for polymer purification and is suitable for automation, which will help to overcome the unsolved and labor-intensive task of purifying (co)polymer libraries derived from high-throughput experimentation.

Identification of Topotactic Surface-Confined Ullmann-Polymerization.

On-surface Ullmann coupling is an established method for the synthesis of 1D and 2D organic structures. A key limitation to obtaining ordered polymers is the uncertainty in the final structure for coupling via random diffusion of reactants over the substrate, which leads to polymorphism and defects. Here, a topotactic polymerization on Cu(110) in a series of differently-halogenated para-phenylenes is identified, where the self-assembled organometallic (OM) reactants of diiodobenzene couple directly into a single, deterministic product, whereas the other precursors follow a diffusion driven reaction. The topotactic mechanism is the result of the structure of the iodine on Cu(110), which controls the orientation of the OM reactants and intermediates to be the same as the final polymer chains. Temperature-programmed X-ray photoelectron spectroscopy and kinetic modeling reflect the differences in the polymerization regimes, and the effects of the OM chain alignments and halogens are disentangled by Nudged Elastic Band calculations. It is found that the repulsion or attraction between chains and halogens drive the polymerization to be either diffusive or topotactic. These results provide detailed insights into on-surface reaction mechanisms and prove the possibility of harnessing topotactic reactions in surface-confined Ullmann polymerization.

AIE Effect by Oxygen Clustering in Vegetable Oil‐Based Polymers

AbstractVegetable oil has been widely used to synthesize monomers and polymers in different fields. Some authors have found different polymers in maleinized vegetable oil; however, they have not described the luminescent properties of the polymers in an intensive way. This work aimed to synthesize new polymers from macadamia oil using diethylene glycol and glycerol as crosslinkers and their characterization The results obtained by spectroscopic analyses confirmed the incorporation of anhydride, as well as the reactions for the final polymers. Results from UV‐Vis showed that maleinized macadamia oil presented an aggregation‐induced emission effect with solvatochromic effect with absorption at 201.6 nm (ethanol) and 241.8 nm (chloroform), which was corroborated by theoretical calculations. Moreover, the luminescent property exhibited by both obtained polymers was kept even after the swelling test, and powdering the samples. Therefore, these polymers, synthetized in a fast way and without catalyst, open a new field of renewable and sustainable materials with luminescent properties that can be applied in technological fields, such as solar cells and fluorescent sensors.

Terpolymerization of CO2 with Epoxides and Cyclic Organic Anhydrides or Cyclic Esters

The synthesis of polymeric materials starting from CO2 as a feedstock is an active task of research. In particular, the copolymerization of CO2 with epoxides via ring-opening copolymerization (ROCOP) offers a simple, efficient route to synthesize aliphatic polycarbonates (APC). In many cases, APC display poor physical and chemical properties, limiting their range of application. The terpolymerization of CO2 with epoxides and organic anhydrides or cyclic esters offers the possibility, combining the ROCOP with ring-opening polymerization (ROP), to access a wide range of materials containing polycarbonate and polyester segments along the polymer chain, showing enhanced properties with respect to the simple APC. This review will cover the last advancements in the field, evidencing the crucial role of the catalytic system in determining the microstructural features of the final polymer.

Efficient Design to Monitor the Site‐specific Sustained Release of a Non‐Emissive Anticancer Drug

A pH-responsive smart nanocarrier with significant components was synthesized by conjugating the non-emissive anticancer drug methyl orange and polyethylene glycol derived folate moiety to the backbone of polynorbornene. Complete synthesis procedure and characterization methods of three monomers included in the work: norbornene-derived Chlorambucil (Monomer 1), norbornene grafted with polyethylene glycol, and folic acid (Monomer 2) and norbornene attached methyl orange (Monomer 3) connected to the norbornene backbone through ester linkage were clearly discussed. Finally, the random copolymer CHO PEG FOL METH was synthesized by ring-opening metathesis polymerization (ROMP) using Grubbs' second-generation catalyst. Advanced polymer chromatography (APC) was used to find the final polymer's molecular weight and polydispersity index (PDI). Dynamic light scattering, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were utilized to explore the prodrug's size and morphology. Release experiments of the anticancer drug, Chlorambucil and the coloring agent, methyl orange, were performed at different pH and time. Cell viability assay was carried out for determining the rate of survived cells, followed by the treatment of our final polymer named CHO PEG FOL METH.

Recent progress in self-healing polyurethanes based on Diels-Alder reaction

This review examines the latest advances in the synthesis and application of polyurethanes that have a self-healing effect due to the thermally reversible Diels-Alder reaction. A classification of strategies for improving the parameters of the final polymers is proposed, which includes the division into polyurethanes with a flexible organic linker, composites with nanoparticles, and systems with a dual self-healing mechanism both due to the Diels-Alder reaction and the reaction of the formation of a disulfide bonds from thiols. The possible applications of the obtained materials and the assumption about the further development of the field are considered.

Copper-catalyzed ARGET ATRP of styrene from ethyl α-haloisobutyrate in EtOAc/EtOH, using ascorbic acid/Na2CO3 as reducing system

Atom transfer radical polymerization (ATRP) is one of the most powerful techniques to synthesize precisely tailored polymers and macrostructures. Activators regenerated by electron transfer (ARGET) ATRP was developed as a “green” strategy to decrease the load of the metal catalyst. However, ARGET ATRP usually uses not-so-green reducing agents (e.g. Sn2+) or expensive and industrially impractical procedures. For these reasons, we report an ARGET ATRP of styrene with various carbonates as reducing agents, both alone and paired with ascorbic acid (AA), using monofunctional initiators and Cl or Br as exchanging atoms. The solvent mixture is composed of the green combination of EtOAc and EtOH, even in the presence of modest amounts of H2O. Cyclic voltammetry was used to evaluate the effect of H2O on the catalyst, as well as the absence of AA. The system returned high yields and low dispersities with low amounts of catalyst (~60 ppm) and moderate reaction times. Excellent results were obtained only with the Cl-ATRP system. NMR spectroscopy and kinetic analyses proved the livingness of the final polymer chains.