Polymerization Solvent Research Articles

Nonspherical Liquid Crystalline Assemblies with Programmable Shape Transformation.

Liquid crystalline (LC) assemblies with tailored shape and programmable shape transformation were prepared via polymerization-induced self-assembly. The influence of polymerization temperature and solvent on the shape of the LC assemblies indicated that shape of the LC assemblies could be delicately regulated by the repulsive interaction among the solvophilic chains and LC ordering. Programmable shape transformation of ellipsoidal LC assemblies was achieved, taking advantage of the smectic-to-isotropic phase transition. The ellipsoidal assemblies could remain ellipsoids or transform to faceted spheres and spheres, depending on the temperature procedure used. Besides, the generated spheres could be reshaped to ellipsoids with high shape recovery ratio. Small angle X-ray scattering study indicated that the interplay of the reversible smectic-to-isotropic phase transition and kinetic trapping underpins the programmed shape transformation. As a general approach to LC assemblies with programmable shape transformation, our strategy would provide a reliable platform for nanoactuators, nanomotors, and adaptive colloidal devices.

A Poly(ionic liquid) Gel Electrolyte for Efficient all Solid Electrochemical Double-Layer Capacitor

Polyionic liquid based gels have stimulated significant interest due to their wide applications in flexible electronics, such as wearable electronics, roll-up displays, smart mobile devices and implantable biosensors. Novel supported liquid gel electrolyte using polymerisable ionic liquid and an acrylate monomer, has been developed in this work by entrapping ionic liquid during polymerisation instead of post polymerisation impregnation. The chemically crosslinked polyionic liquid gel electrolyte (PIL) is prepared using 2-hydroxyethylmethacrylate (HEMA) monomer and a polymerisable ionic liquid, 1,4-di(vinylimidazolium)butane bisbromide (DVIMBr) in an ionic liquid (IL- 1-butyl-3 methylimidazolium hexafluorophosphate) as the polymerisation solvent, which resulted in in-situ entrapment of the IL in the gel during polymerisation and crosslinking of the polymer. The supported liquid gel electrolyte (SLG) material was characterised with thermal analysis, infrared spectroscopy, and dynamic mechanical analysis, and was found to be stable with good mechanical properties. The electrochemical analysis showed that these chemically cross-linked PIL gel electrolyte-supported ILs are suitable for solid-state, flexible supercapacitor applications.

Unraveling Mechanisms of Chiral Induction in Double-Helical Metallopolymers.

Self-assembled helical polymers hold great promise as new functional materials, where helical handedness controls useful properties such as circularly polarized light emission or electron spin. The technique of subcomponent self-assembly can generate helical polymers from readily prepared monomers. Here we present three distinct strategies for chiral induction in double-helical metallopolymers prepared via subcomponent self-assembly: (1) employing an enantiopure monomer, (2) polymerization in a chiral solvent, (3) using an enantiopure initiating group. Kinetic and thermodynamic models were developed to describe the polymer growth mechanisms and quantify the strength of chiral induction, respectively. We found the degree of chiral induction to vary as a function of polymer length. Ordered, rod-like aggregates more than 70 nm long were also observed in the solid state. Our findings provide a basis to choose the most suitable method of chiral induction based on length, regiochemical, and stereochemical requirements, allowing stereochemical control to be established in easily accessible ways.

In Situ Complex with by-product HCl and Release Chloride Ions to Dissolve Aramid.

Because of the strong hydrogen-bond interaction among macromolecular chains, the addition of chloride salts is generally needed to offer Cl- ions for the dissolution of aromatic polyamides. In this paper, poly-(benzimidazole-terephthalamide) which complexed with by-product HCl during polymerization (PABI-HCl) was prepared and imidazole compound as cosolvent was added into dimethylacetamide (DMAc) to dissolve PABI-HCl. Due to stronger affinity to protons, imidazole compound could in-situ complex with HCl of PABI-HCl and form imidazolium hydrochloride. Then imidazolium hydrochloride would ionize and produce much free Cl- ions which acted as stronger hydrogen-bond acceptor to disrupt interaction among macromolecular chains. As a result, solubility of PABI-HCl in DMAc was improved significantly in existence of small amount of imidazole compound. Moreover, DMAc-imidazole mixture was utlized for synthesis of different kinds of aramids and no precipitation was observed with progress of the reaction. So the mixture was suitable to be utlized as solvent for polymerization of aramid.

Controlled Polymerization in Polar Solvents to Ultrahigh Molecular Weight Polyethylene.

Novel complexes based on 2,4,8-triarylnaphthylamine [[(2,4-{3,5-(CF3)2C6H3}2-8-(3,5-R2C6H3)-C10H4)-N═C(H)-{3-(9-anthryl)-2-O-C6H3}-κ2-N,O]Ni(CH3)(pyridine)] (4-Py, R = Me; 5-Py, R = CF3) were synthesized from 8-arylnaphthylamines which can be generated via selective lithiation, borylation, and coupling in a one-pot procedure. Due to their living characteristics in ethylene polymerization and the particularly low propensity of 5-Py for β-H elimination as reflected by a high linearity even at elevated polymerization temperatures of 60 °C, ultrahigh molecular weight polyethylene (UHMWPE) is formed in polar organic solvents (THF, diethyl ether) as a reaction medium in a controlled polymerization ( Mw/ Mn = 1.2 at Mn = 1.1 × 106 g mol-1).

Stereoselective Ring-Opening Polymerization of rac-Lactide Using Organocatalytic Cyclic Trimeric Phosphazene Base

Phosphazene base is an important organocatalyst in polymer chemistry owing to its high activity and versatility. In this contribution, we demonstrate that cyclic trimeric phosphazene base (CTPB) can catalyze stereoselective ring-opening polymerization (ROP) of rac-lactide (rac-LA) to produce isotactic stereoblock PLA (Pi up to 0.93). The polymerizations are highly controlled, as evidenced by linear relationship between molecular weights (MW) and monomer conversions and the narrow dispersity (Đ = Mw/Mn) of the resulted polymers with high fidelity of end groups. The investigations on polymerization parameters show that the tacticity of produced PLA depends on the polymerization temperatures and solvents, while the kinetic studies reveal a faster rate for ROP of l-LA as compared to rac-LA under same conditions. Based on these results, the chain end control mechanism is proposed to explain the production of isotactic stereoblock PLA from rac-LA by an achiral catalyst.

A Highly Efficient Aromatic Amine Ligand/Copper(I) Chloride Catalyst System for the Synthesis of Poly(2,6-dimethyl-1,4-phenylene ether).

Highly active catalyst systems for polymerizing 2,6-dimethylphenol were studied by using aromatic amine ligands and copper(I) chloride. The aromatic amine ligands employed were pyridine, 1-methylimidazole, 2-aminopyridine, 3-aminopyridine, and 4-aminopyridine. A mixture of chloroform and methanol (9:1, v/v) was used as a polymerization solvent. All experiments were performed with oxygen uptake measurement apparatus, while the reaction rate for each aromatic amine ligand-Cu catalyst system and the amount of by-product, 3,3′,5,5′-Tetramethyl-4,4′diphenoquinone (DPQ), were measured to determine the efficiency of the catalyst systems. The 4-aminopyridine/Cu (I) catalyst system was found to be extremely efficient in poly(2,6-dimethyl-1,4-phenylene ether) (PPE) synthesis; it had the fastest reaction rate of 6.98 × 10−4 mol/L·s and the lowest DPQ production. The relatively high basicity of 4-aminopyridne and the less steric hindrance arising from a coordination of Cu and 4-aminopyridine in this catalyst are responsible for the fast polymerization rate. When 2-aminoprydine (an isomer of 4-aminopyridine) was used as a ligand, however, no polymerization occurred probably due to steric hindrance.

Synthesis of Highly Regioregular, Head-to-Tail Coupled Poly(3-octylesterthiophene) via C—H/C—H Coupling Polycondensation

Highly regioregular, head-to-tail coupled poly(3-octylesterthiophene) was synthesized by the Pd-catalysed oxidative C—H/C—H coupling polycondensation. The regioregularity of polymer products was confirmed by the 1H-NMR technique. Furthermore, the effects of various reaction factors including polymerization temperature, solvents and catalysts etc. on the yield, molecular weight and structural regioregularity of the resultant polymers were systematically studied. The optical, electrochemical and crystallization properties of the resultant P3OET with different HT regioregularities in solution and film state were studied by UV-Vis and fluorescent spectroscopy, cyclic voltammetry and X-ray diffraction (XRD), resepectively.

Open-to-Air RAFT Polymerization in Complex Solvents: From Whisky to Fermentation Broth.

We investigate the use of in situ enzyme degassing to facilitate the open-to-air reversible addition-fragmentation chain transfer (RAFT) polymerization of hydroxyethyl acrylate (HEA) in a wide range of complex aqueous solvents, including, beer, wine, liquor, and fermentation broth. This enzyme-assisted polymerization procedure is impressively robust, and poly(HEA) was attained with good control over molecular weight and a narrow dispersity in nearly all of the solvents tested. Kinetics experiments on HEA polymerization in whisky and spectroscopic analysis of the purified polymers suggest high end-group fidelity, as does the successful chain extension of a poly(HEA) macro chain transfer agent with narrow dispersity. These results suggest enzyme-assisted RAFT may be a powerful and underutilized tool for high-throughput screening and materials discovery and may simplify the synthesis of well-defined polymers in complex conditions.

Synthesis of high‐solid‐content, acrylic pressure‐sensitive adhesives by solvent polymerization

ABSTRACTIn this study, we prepared high solid content (SC), solvent‐based, acrylic pressure‐sensitive adhesives (PSAs) with n‐dodecyl mercaptan as a chain‐transfer agent (CTA) and studied the crosslinking reactions between the crosslinker and the acrylic PSAs. Acrylic PSAs were prepared from 2‐ethyl hexyl acrylate, acrylic acid (AA), and 2‐azobisisobutyronitrile with a solution polymerization process. The results show AA resulted in an effective molecular weight in the acrylic PSAs, as it improved the hydrophilicity with increasing peel strength of the acrylic PSAs. As for the high SC, the molecular weight and system viscosity decreased through the addition of CTA. At a constant AA amount, the addition of CTA decreased the molecular weight and increased the hydrophobicity of the acrylic PSAs; this decreased the peel strength of the acrylic PSAs on the glass. Furthermore, the addition of CTA decreased the molecular weight and improved the acrylic PSAs' surface morphologies and optical properties. The acrylic PSAs produced in this study could meet production needs. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46257.

Investigation of green and sustainable solvents for direct arylation polymerization (DArP)

Green solvents, notably cyclopentyl methylether (CPME), are found to be highly effective in Direct Arylation Polymerization (DArP).

Semi‐interpenetrating polymer networks based on crosslinked poly(N‐isopropyl acrylamide) and methylcellulose prepared by frontal polymerization

ABSTRACTIn this work, semi‐interpenetrating gels of poly(N‐isopropyl acrylamide) and methylcellulose were successfully synthesized by using the Frontal Polymerization (FP) technique. The gels were obtained in the presence of dimethyl sulfoxide and trihexyltetradecylphosphonium persulfate, as polymerization solvent and radical initiator, respectively, hence avoiding the formation of bubbles during polymerization. Then, some of the gels containing dimethyl sulfoxide were thoroughly washed with water, hence obtaining the corresponding hydrogels. The effects of the ratio between poly(N‐isopropyl acrylamide) and methylcellulose, the amount of crosslinker and solvent medium (i.e., dimethyl sulfoxide and water) were thoroughly studied, assessing the influence of temperature and velocity of FP fronts on the glass transition temperature values (dried samples), on the swelling behavior and on the dynamic‐mechanical properties (gels swollen both in water and dimethyl sulfoxide). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 437–443

Self‐assembly of block copolymers with an alkoxysilane‐based core‐forming block: A comparison of synthetic approaches

ABSTRACTPolymerization‐induced self‐assembly (PISA) has become the preferred method of preparing self‐assembled nano‐objects based on amphiphilic block copolymers. The PISA methodology has also been extended to the realization of colloidal nanocomposites, such as polymer–silica hybrid particles. In this work, we compare two methods to prepare nanoparticles based on self‐assembly of block copolymers bearing a core‐forming block with a reactive alkoxysilane moiety (3‐(trimethoxysilyl)propyl methacrylate, MPS), namely (i) RAFT emulsion polymerization using a hydrophilic macroRAFT agent and (ii) solution‐phase self‐assembly upon slow addition of a selective solvent. Emulsion polymerization under both ab initio and seeded conditions were studied, as well the use of different initiating systems. Effective and reproducible chain extension (and hence PISA) of MPS via thermally initiated RAFT emulsion polymerization was compromised due to the hydrolysis and polycondensation of MPS occurring under the reaction conditions employed. A more successful approach to block copolymer self‐assembly was achieved via polymerization in a good solvent for both blocks (1,4‐dioxane) followed by the slow addition of water, yielding spherical nanoparticles that increased in size as the length of the solvophobic block was increased. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 420–429

Strategy for rational control of stereosequence in free radical polymerization of acrylates

ABSTRACTRadical polymerization of cyclic analogs of acrylates, (S)‐ and (R)‐2‐isopropyl‐5‐methylene‐1,3‐dioxolan‐4‐ones (1S and 1R), successfully afforded a functional polymer having the tacticity continuously controlled from 29% to ∼100% of meso triad (mm) over a wide range of temperature only by changing the molar ratio of 1S/1R in feed. Plot of the number fractions of the triad versus diad of poly(1) was in good agreement with the Bernoulli statistics. In the polymerization in chiral solvents having analogs structure of the monomers, the tacticity and specific rotation of the resulting polymer were specifically varied depending on the structure and concentration of the solvents. Model propagation reaction at dimeric radical calculated with density functional theory reproduced a methodical induction of the chirality to the main chain from the branched chiral monomeric unit, which supports the experimental expectations. It is remarkable that the ceiling temperature of 1 is tremendously high, for example, 193 °C in [1 (ee = 72.6%)] = 0.05 mol/L, and the isospecific polymerization is maintained even at such a high temperature, which enabled the control of polymer tacticity over a wide range of temperature. The mechanism of the stereosequence in radical polymerization was discussed experimentally and theoretically. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 184–193

Synthesis and modification of poly(ethyl 2-(imidazol-1-yl)acrylate) (PEImA)

We present the synthesis and characterization of poly(ethyl 2-(imidazol-1-yl)acrylate) (PEImA) using free radical polymerization in various solvents with and without acids as additive. In addition, PEImA was also prepared using anionic polymerization with KOtBu as initiator in DMF and in THF at different M:I ratios. The resulting polymers of moderate dispersity were characterized by 1H-NMR, solid state 13C-NMR, and size exclusion chromatography (SEC) both in water and DMAc. PEImA is an interesting highly substituted polymer as it can be modified by methylation to poly(ethyl 2-(methyl imidazolium-1-yl iodide)acrylate) PEMeImA, via ester cleavage into the polyzwitterion poly(2-(imidazol-1-yl)acrylic acid) (PImAA), and – finally - to poly(2-(methyl imidazolium-1-yl)acrylic acid) (PMeImAA) if both modification steps are carried out. We also investigated structure and solubility of these different polyelectrolytes using potentiometric titration in aqueous media.

Comparative Investigations on Optimum Polymerization Conditions for the Synthesis of a Sustainable Poly(Lactic Acid)

The development of synthetic biodegradable polymers using solvent free polymerization has a unique potential to be used as sustainable polymers in biomedical applications. The aim of this work was to synthesize and characterize a sustainable class of poly(lactic acid) (PLA) under different operating conditions via direct polycondensation of lactic acid (LA). Several parameters were tested including the absence of solvents and catalysts on the polymerization, in addition to polymerization temperature and time. Polymerization conditions were evaluated using response surface method (RSM) to optimize the impact of temperature, time, and catalyst. Results showed that molecular weight (Mw) of PLA increased with increasing polymerization time. Highest Mw of 28.4 kD with relatively a broad polydispersity 1.9 was achieved at polymerization temperature 170 °C at 24 h in the free solvent polymerization. This led to a relevant inherent viscosity of 0.37 dl/g. FTIR spectra exhibited a disappearance of the characteristic peak of the hydroxyl group in LA at 3482 cm−1 by increasing the intensity of carbonyl group. The 1H nuclear magnetic resonance (NMR) exhibited the main chain at 5.22 ppm and the signal of methyl proton at 1.61 ppm as well as a signal at 4.33 and 1.5 assigned to the methane proton next to the terminal hydroxyl group and carboxyl group respectively. Meanwhile, the PLA synthesized with a catalyst [Sn(Oct)2] in a free solvent demonstrated comparatively high thermal transition properties of glass transition, melting, and crystallinity temperatures of 48, 106, and 158 °C, respectively. These results are of significant interest to further expand the use of PLA in biomedical applications.

Solvent-Selective Reactions of Alkyl Iodide with Sodium Azide for Radical Generation and Azide Substitution and Their Application to One-Pot Synthesis of Chain-End-Functionalized Polymers.

Herein, a new reaction of an alkyl iodide (R-I) with an azide anion (N3-) to reversibly generate the corresponding alkyl radical (R•) is reported. Via this new reaction, N3- was used as an efficient catalyst in living radical polymerization, yielding a well-defined polymer-iodide. A particularly interesting finding was the solvent selectivity of this reaction; namely, R-I and N3- generated R• in nonpolar solvents, while the substitution product R-N3 was generated in polar solvents. Exploiting this unique solvent selectivity, a one-pot synthesis of polymer-N3 was attained. N3- was first used as a catalyst for living radical polymerization in a nonpolar solvent to produce a polymer-iodide and was subsequently used as a substitution agent in a polar solvent by simply adding the polar solvent, thereby transforming the polymer-iodide to polymer-N3 in one pot. This one-pot synthesis was further applied to obtain N3-chain-end-functionalized polymer brushes on the surface, uniquely controlling the N3 coverage (number density). Using the chain-end N3, the obtained linear and brush polymers were connected to functional molecules via an azide-alkyne click reaction. The attractive features of this system include facile operation, access to unique polymer designs, and no requirement for using excess NaN3. In addition to N3-, thiocyanate (-SCN) and cyanate (-OCN) anions were also studied.

Water and Carbon Dioxide: A Unique Solvent for the Catalytic Polymerization of Ethylene in Miniemulsion

The catalytic polymerization of ethylene is performed in water pressurized with CO2 . The size of the initial monomer droplets and of the resulting polymer particles can be varied by simply changing the CO2 pressure. Furthermore, at identical ethylene partial pressure, the polymerizations performed in the presence of CO2 are significantly faster than in its absence. Thus, the combination of CO2 and water is a promising green solvent for catalytic emulsion polymerizations.

High yield preparation of uniform polyurea microspheres through precipitation polymerization and their application as laccase immobilization support

Uniform polyurea (PU) microspheres were prepared through precipitation polymerization using isophorone diisocyanate (IPDI) as the only monomer in mixed solvent of water-acetonitrile. The highest IPDI loading allowed to have uniform PU microspheres went up to 23wt%, with a high yield of about 95% for the microspheres. The productivity of microspheres thus obtained was about 22 times higher than that by free radical precipitation polymerization, and practically doubled that previously reported on the same polymerization in the mixed solvent of water-acetone. In addition, the polymerization was done under quiescent process with the reactor standing still without any stirring or shaking. TGA and FTIR tests indicated that the microspheres were of high thermal stability with abundant amine group on the surface. As a model enzyme, laccase was immobilized on the surface of the PU microspheres via glutaraldehyde coupling. Compared with the free laccase, the immobilized one exhibited higher activity in alkaline environment and higher thermal stability. The immobilized laccase was used as biocatalyst for degradation of Remazol Brilliant Blue R and showed good decolorization capacity with good reusability. About 65% of its initial catalytic activity was retained after 7 cycles of reuse. This work provides a practically operational protocol for large scale production of uniform PU microspheres, and also demonstrates that these microspheres have promising applications as enzyme immobilization carrier and as biocatalyst in organic dyes degradation.

Effect of sodium hydroxide solution as polymerization solvent and activator on structural, mechanical and antibacterial properties of PNIPAAm and P(NIPAAm–clay) hydrogels

Poly(N‐isopropylacrylamide) (PNIPAAm) and its composite hydrogels were synthesized by free‐radical polymerizations in NaOH solutions (0.1, 0.2 N). Laponite (LP), Montmorillonite (MMT) and ODA(octadecylamine)‐MMT were used as inorganic multicrosslinkers while BIS was chosen as conventional crosslinker. All polymerizations were initiated with KPS alone. The effects of two different concentrations of NaOH‐KPS redox pair and long reaction times (1w and 2w) at 25°C on structural and mechanical properties, antibacterial and haemolytic activities of the modified hydrogels were studied by conductometric titrations, FTIR, XRD, EDX, compression, inhibition zone and haemolysis tests. Their homogenities, compressive moduli at 37°C, antibacterial activities and blood compatibilities increased with increasing reaction time and NaOH concentration. POLYM. COMPOS., 39:E386–E406, 2018. © 2017 Society of Plastics Engineers