Conventional Free Radical Copolymerization Research Articles

Comparison of gels synthesized by controlled radical copolymerization and free radical copolymerization: molecular dynamics simulation.

The structures of gels synthesized by controlled radical copolymerization (CRP) and conventional free radical copolymerization (FRP) were studied by a coarse-grained molecular dynamics simulation. It was confirmed that the CRP gel has a larger number of elastically effective chains and fewer cyclic structures and entanglements than the FRP gel, i.e., the network structure of the CRP gel is more uniform than that of the FRP gel. However, the difference in the shear modulus between the two gels was small due to the opposing changes in the number of elastically effective chains and that of entanglements. The relatively uniform structure of the CRP gel is attributed to the suppression of intramolecular cross-linking by the fast initiation and slow propagation, and the development of cross-linked structures in the post-gel region due to the limited termination. The effects of these CRP characteristics were studied in detail. From the results, it was found that all of these characteristics of CRP cooperatively act to improve the homogeneity of the structure of the CRP gel.

Preparation and Characterization of a Preformed Polyampholyte Particle Gel Composite for Conformance Control in Oil Recovery.

Preformed particle gels (PPGs) based on acrylamide (AAm), (3-acrylamidopropyl) trimethylammonium chloride (APTAC), and 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPS) were synthesized via conventional free radical copolymerization. The resultant PPGs of various compositions were characterized using FTIR spectroscopy, TG and DT analysis, and mechanical testing. The swelling behavior of PPGs depending on ionic strength, temperature, degree of crosslinking, and pH was also studied. The obtained results show that the swelling mechanism of PPGs is mainly due to the diffusion of the solvent. The mechanical properties of PPGs were improved by creating a composite polymer network by adding the clay mineral (bentonite) to the reaction mixture of monomers, which also makes it possible to control the Young's modulus and the swelling degree of the samples.

Guanine and cytosine‐containing acrylic supramolecular networks

AbstractThis manuscript describes the synthesis and characterization of guanine and cytosine‐containing supramolecular copolymers, which are inspired from the guanine and cytosine nucleobase pair in deoxyribonucleic acid. Regioselective Michael‐addition allowed the efficient installation of the nucleobases on acrylate‐containing monomers, which enabled the preparation of a series of nucleobase‐functionalized acrylate and n‐butyl acrylate copolymers using conventional free radical copolymerization. Guanine‐containing copolymers exhibited superior thermal properties, thermomechanical performance, and more defined morphological structure than cytosine‐containing copolymer analogs due to the relatively strong guanine self‐association, thus expanding the potential applications for mechanically reinforced polymeric networks. Blending guanine‐ and cytosine‐containing copolymers formed a supramolecular structure through multiple hydrogen bonding between guanine and cytosine units. The supramolecular blend exhibited intermediate thermomechanical and morphological properties, which suggested that guanine and cytosine units were not fully associated in the random copolymer composition. This work provides valuable fundamental understanding of structure–property‐morphology relationships in acrylic copolymers with the presence of guanine‐cytosine self‐ and complementary interactions, suggesting new understanding in supramolecular design for enhanced mechanical and morphological properties.

Hydrocarbon-Based Statistical Copolymers Outperform Block Copolymers for Stabilization of Ethanol–Water Foams

Well-defined block copolymers have been widely used as emulsifiers, stabilizers, and dispersants in the chemical industry for at least 50 years. In contrast, nature employs amphiphilic proteins as polymeric surfactants whereby the spatial distribution of hydrophilic and hydrophobic amino acids within the polypeptide chains is optimized for surface activity. Herein, we report that polydisperse statistical copolymers prepared by conventional free-radical copolymerization can provide superior foaming performance compared to the analogous diblock copolymers. A series of predominantly (meth)acrylic comonomers are screened to identify optimal surface activity for foam stabilization of aqueous ethanol solutions. In particular, all-acrylic statistical copolymers comprising trimethylhexyl acrylate and poly(ethylene glycol) acrylate, P(TMHA-stat-PEGA), confer strong foamability and also lower the surface tension of a range of ethanol–water mixtures to a greater extent than the analogous block copolymers. For ethanol-rich hand sanitizer formulations, foam stabilization is normally achieved using environmentally persistent silicone-based copolymers or fluorinated surfactants. Herein, the best-performing fully hydrocarbon-based copolymer surfactants effectively stabilize ethanol-rich foams by a mechanism that resembles that of naturally-occurring proteins. This ability to reduce the surface tension of low-surface-energy liquids suggests a wide range of potential commercial applications.

Temperature and Salt Responsive Amphoteric Nanogels Based on N-Isopropylacrylamide, 2-Acrylamido-2-methyl-1-propanesulfonic Acid Sodium Salt and (3-Acrylamidopropyl) Trimethylammonium Chloride.

Polyampholyte nanogels based on N-isopropylacrylamide (NIPAM), (3-acrylamidopropyl) trimethylammonium chloride (APTAC) and 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPS) were synthesized via conventional redox-initiated free radical copolymerization. The resultant nanogels of various compositions, specifically [NIPAM]:[APTAC]:[AMPS] = 90:5:5; 90:7.5:2.5; 90:2.5:7.5 mol.%, herein abbreviated as NIPAM90-APTAC5-AMPS5, NIPAM90-APTAC7.5-AMPS2.5 and NIPAM90-APTAC2.5-AMPS7.5, were characterized by a combination of 1H NMR and FTIR spectroscopy, TGA, UV–Vis, DLS and zeta potential measurements. The temperature and salt-responsive properties of amphoteric nanogels were studied in aqueous and saline solutions in a temperature range from 25 to 60 °C and at ionic strengths (μ) of 10−3 to 1M NaCl. Volume phase transition temperatures (VPTT) of the charge-balanced nanogel were found to reach a maximum upon the addition of salt, whereas the same parameter for the charge-imbalanced nanogels exhibited a sharp decrease at higher saline concentrations. A wide bimodal distribution of average hydrodynamic sizes of nanogel particles had a tendency to transform to a narrow monomodal peak at elevated temperatures and higher ionic strengths. According to the DLS results, increasing ionic strength results in the clumping of nanogel particles.

Immobilization of Methyl Orange and Methylene Blue within the Matrix of Charge-Imbalanced Amphoteric Nanogels and Study of Dye Release Kinetics as a Function of Temperature and Ionic Strength

Cross-linked polyampholyte nanogels consisting of neutral N-isopropylacrylamide (NIPAM), negatively charged sodium salt of 2-acrylamido-2-methylpropanesulfonate (AMPS), and positively charged (3-acryl-amidopropyltrimethylammonium chloride (APTAC) monomers were synthesized via conventional redox ini-tiated free radical copolymerization using N,N-methylenebis(acrylamide) (MBAA) as a cross-linking agent. The resulting nanogels were characterized by means of FTIR and 1H NMR spectroscopy, dynamic light scat-tering (DLS) and zeta-potential measurements. Surface morphology was analyzed using scanning electron microscopy. Due to the presence of thermally responsive NIPAM units and varying molar ratios of anionic (AMPS) and cationic (APTAC) units, the resulting nanogels were responsive to multiple stimuli in aqueous media and can be used for controlled delivery of dyes. Thus, the NIPAM90-APTAC7.5-AMPS2.5 nanogel with an excess of the cationic units was chosen for immobilization of the anionic dye, methyl orange (MO), whereas the NIPAM90-APTAC2.5-AMPS7.5 nanogel with an excess of the anionic units was chosen for immo-bilization of the cationic dye, methylene blue (MB). The release kinetics of the dyes from the nanogel was studied depending on the phase transition temperature and the salt content. Mechanism of the dye release from the nanogel matrix was determined using the Ritger-Peppas equation. Disappearance of the ionic con-tacts between the charged groups of the nanogels and the ionic dyes was suggested to be the main reason for the diffusion of the dyes through the dialysis membrane into the external solution.

Photocurable selenophene/maleimide-based high-refractive-index copolymers obtained via radical copolymerization

Selenophene-containing copolymers with either alternating or random sequences and high refractive indices were synthesized via conventional free-radical copolymerization of 2-vinylselenophene (2VS). Copolymers with a moderate alternating tendency were obtained via radical copolymerization of electron-donating 2VS and electron-accepting maleimide derivatives, such as N-methyl maleimide (MMI), N-phenyl maleimide (PMI), and N-vinyl maleimide (VMI). Copolymerization of 2VS with glycidyl methacrylate (GMA) also afforded copolymers containing selenophene and reactive epoxy units in the side chains. The selenophene-containing poly(2VS) showed a high refractive index (1.6420 @ 589 nm) and a reasonable Abbe number (30.7). High refractive indices of 1.6138–1.5959 with corresponding Abbe numbers of ~30 were similarly achieved for the selenophene/maleimide copolymers. The introduction of the maleimide moiety into the polymer side chain improved its thermal stability (Td5 > 320 °C) and enhanced the glass transition temperature (Tg = 158–160 °C). Selenophene-containing copolymers with pendant N-vinyl units were obtained via copolymerization of 2VS and VMI, which was successfully employed as a precursor for obtaining a photoinduced crosslinked film via a thiol-ene reaction with 1,6-hexanedithiol in the presence of a photo-radical initiator under ultraviolet irradiation. Thus, for the first time, photocurable and high-refractive-index selenophene-based copolymers were developed through the combination of a selenophene-containing vinyl monomer and a maleimide derivative with a pendant N-vinyl group.

Synthesis and characterization of novel acrylamide-based ternary polyampholyte as tracer agent

A novel ternary polyampholyte composed of fully charged anionic monomer – 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPS), cationic monomer – (3-acrylamidopropyl) trimethylammonium chloride (APTAC) and the positively charged fluorescent dye – acrylamide Nile Blue (ANB) was synthesized by conventional free radical copolymerization and characterized by FTIR, UV-Vis, fluorescence spectroscopy, dynamic light scattering and zeta-potential. FTIR spectrum of AMPS-APTAC-ANB shows that introduction of 1 mol.% ANB into copolymer composition does not influence the basic characteristic bands of polyampholyte. The adsorption and emission peaks of AMPS-APTAC-ANB found at max = 586 nm and max = 660-680 nm are attributed to ANB groups of terpolymer. The average hydrodynamic size and zeta potential of AMPS-APTAC-ANB in aqueous solution that are equal to 4.3 nm and = 1.6 mV indicating the globular conformation of amphoteric macromolecules with a slightly negative charge. Injection of 0.1 wt.% (or 1.310-3 molL-1) AMPS-APTAC-ANB into the core sample derived from the “Vostochnyi Moldabek” oilfield demonstrated the passing of fluorescently-labeled terpolymer through the core. The ternary polyampholyte containing the fluorescent marker can serve as oilfield tracer for monitoring well-to-well connections (or interwell tracer test).

Suspension stability control using light-sensitive polymers

In this paper a novel approach to the flocculation phenomenon was investigated, i.e. application of light-sensitive polymers. A hypothesis was proposed that the energy delivered by an electromagnetic wave will trigger the photo-dimerization reaction, which in turn will lead to the destabilization process via bridging phenomenon. In research two polymers differing in content of light-sensitive component, i.e. cinnamoyl groups, were synthesized by means of conventional free radical copolymerization and postreaction. In the flocculation experiments a model suspension of CaCO3 precipitate in deionized water was used. The experiments were performed using two different mixer configurations. Unfortunately, the postulated mechanism was proved to be wrong. Although both polymers acted as good destabilization agents directly after injection to suspension, the UV radiation had no impact on the process.

A facile synthesis of thermo-responsive copolymer stabilized fluorescent silver nanoclusters and their application in pH sensing

Luminescent silver nanoclusters (NCs) decorated with temperature-responsive copolymer P(NIPAm-co-MQ) have been fabricated in aqueous solution as a new fluorescent pH stimuli-responsive functional materials. P(NIPAm-co-MQ) was prepared by a conventional free-radical copolymerization of isopropylacrylamide (NIPAm) as thermo-responsive units and 5-(2-methacryloylethyloxymethyl)-8-quinolinol (MQ) as coordinating groups. The obtained fluorescent Ag NCs with various sizes showed different morphologies from single sphere to chain structure induced by the copolymer ligand. Upon changing the temperature, the fluorescence intensity of the Ag NCs exhibited temperature triggered response simultaneously. The copolymer stabilized Ag NCs as a pH probe exhibited reversible pH-dependent PL properties over the pH range of 3.04–5.25. With the pH decreased, the fluorescence intensity of Ag NCs under a UV lamp decreased and it was almost completely quenched after pH 3.04. Also, the properties of this fluorescence change with pH are reversible.

Comparison of Polymer Networks Synthesized by Conventional Free Radical and RAFT Copolymerization Processes in Supercritical Carbon Dioxide

There is a debate in the literature on whether or not polymer networks synthesized by reversible deactivation radical polymerization (RDRP) processes, such as reversible addition-fragmentation radical transfer (RAFT) copolymerization of vinyl/divinyl monomers, are less heterogeneous than those synthesized by conventional free radical copolymerization (FRP). In this contribution, the syntheses by FRP and RAFT of hydrogels based on 2-hydroxyethylene methacrylate (HEMA) and ethylene glycol dimethacrylate (EGDMA) in supercritical carbon dioxide (scCO2), using Krytox 157 FSL as the dispersing agent, and the properties of the materials produced, are compared. The materials were characterized by differential scanning calorimetry (DSC), swelling index (SI), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Studies on ciprofloxacin loading and release rate from hydrogels were also carried out. The combined results show that the hydrogels synthesized by FRP and RAFT are significantly different, with apparently less heterogeneity present in the materials synthesized by RAFT copolymerization. A ratio of experimental (Mcexp) to theoretical (Mctheo) molecular weight between crosslinks was established as a quantitative tool to assess the degree of heterogeneity of a polymer network.

Engineering of hemocompatible and antifouling polyethersulfone membranes by blending with heparin-mimicking microgels.

To improve the hemocompatibility and antifouling property of polyethersulfone (PES) membranes, heparin-mimicking microgels of poly(acrylic acid-co-N-vinyl-2-pyrrolidone) (P(AA-VP)) and poly(2-acrylamido-2-methylpropanesulfonic acid-co-acrylamide) (P(AMPS-AM)) were synthesized by conventional free radical copolymerization, and then incorporated into a PES matrix by blending. The results of Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and scanning electron microscopy (SEM) confirmed that heparin-mimicking microgels were successfully synthesized. The presence of the microgels in the membrane matrix was also confirmed by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), and SEM. Compared with pristine PES membranes, the improvement of the antifouling property of the heparin-mimicking microgel modified membranes was demonstrated by the increased flux recovery ratio and improved anti-bacterial adhesion, while the enhancement of hemocompatibility for the modified membranes was proved by the decreased plasma protein adsorption, suppressed platelet adhesion, prolonged clotting times, as well as depressed blood-related complement activation. Additionally, after introducing the heparin-mimicking microgels, the membranes showed enhanced cell adhesion and proliferation properties. These results indicated that the heparin-mimicking microgel modified membranes had great potential to be used as blood contacting materials.

Novel photoreactive phospholipid polymers for preparing a stable biocompatible surface with a smart process

Event Abstract Back to Event Novel photoreactive phospholipid polymers for preparing a stable biocompatible surface with a smart process Tomozumi Noda1*, Masaru Matsuda1*, Nobuyuki Sakamoto1*, Shigeru Kitano1*, Yuuki Inoue2*, Kyoko Fukazawa2* and Kazuhiko Ishihara2* 1 NOF Corporation, Life Sciences Products Division, Japan 2 The University of Tokyo, Department of Materials Engineering, School of Engineering, Japan Introduction: 2-Methacryloyloxyethyl phosphorylcholine (MPC) [1] polymers have been widely applied to some medical devices, including implantable blood pumps, cardiovascular stents and other medical goods. Stabilization of the MPC polymer layer on the substrate is essential issue to solve to have conventional surface treatment. In this study, in order to react the MPC polymer layer to the substrate, we have newly synthesized photoreactive MPC polymers to modify the plastic surface, and evaluated fundamental properties regarding biocompatibility, that is, protein adsorption and cell adhesion. By using these photoreactive MPC polymers, surface treatment is conducted very easy way, such as, coating of the MPC polymer by solvent dipping and after that irradiation light. Materials and Methods: Two types of photoreactive MPC polymers bearing n-butyl methacrylate (BMA) and benzophenone group or phenylazide group were synthesized in a conventional free-radical copolymerization. The presence of benzophenone group (7.20-8.00 ppm ) or phenylazide group (7.10-7.35 ppm and 7.90-8.25ppm) was confirmed by Proton NMR. Each MPC polymer was used for surface modification on various substrates, such as polyethylene and polystyrene, by dip or cast coating, and following the photoirradiation of UV light at 254nm for 7 min. After photoirradiation, all substrates were soaked in ethanol more than 16 h to evaluate reactivity of MPC polymers. The hydrophilic characteristics of the substrates modified with photoreactive MPC polymers were evaluated contact angle measurement by air under water. Then the 96-well polystyrene plates treated with photoreactive MPC polymers were used for examining protein adsorption using peroxidase conjugated antibody and cell adhesion of NIH3T3 cells. Result: Novel photoreactive MPC polymers possessing MPC unit, BMA unit and photoreactive groups were successfully synthesized. The monomer unit fraction of the MPC unit was 60 mol %, BMA unit was 30 mol % and photoreactive group was about 10 mol %. The photoreactive groups were confirmed by 1H-NMR. These polymers can be dissolved in alcohol. Regardless of the kind of the MPC polymers, the treatment resulted in high contact angles of air on the surfaces under water (100 o to 140 o). In addition, protein adsorption and cell adhesion were suppressed. On the other hand, those of the substrates without photoirradiation were equivalent to non-treated substrates in all examinations. Discussion: The substrates treated with the MPC polymers coating and photoirradiation were demonstrated good hydrophilicity even after washing process with ethanol. At this substrate, we observed reduced protein adsorption and cell adhesion. These are one of the fundamental characteristics for making blood-contacting medical devices and implantable devices. These results were due to formation of covalent bonds between the MPC polymers and the substrates and stable surface modification layer was constructed. Conclusion: We developed a smart process to obtain stable and biocompatible surface using photoreactive MPC polymers. The surfaces of various substrates modified with the photoreactive MPC polymer showed super-hydrophilic character, reduction of protein adsorption and inhibition of cell adhesion. Also, the photoreaction with the MPC polymer will be applied to treat a microspace of the substrate. Thus, this excellent anti-biofouling nature will be important to make biocompatible medical devices and biodevices. This research was supported by S-innovation from Japan Agency for Medical Research and Development (AMED)

Multifunctional Hydrogels with Reversible 3D Ordered Macroporous Structures.

Three-dimensionally ordered macroporous (3DOM) hydrogels prepared by colloidal crystals templating display highly reversible shape memory properties, as confirmed by indirect electron microscopy imaging of their inverse replicas and direct nanoscale resolution X-ray microscopy imaging of the hydrated hydrogels. Modifications of functional groups in the 3DOM hydrogels result in various materials with programmed properties for a wide range of applications.

Investigation of proton conductivity of inorganic–organic hybrid membranes based on boronic acid and tetrazole

In this study, proton conducting membranes based on 4-vinyl benzene boronic acid (VBBA) and 5-(methacrylamido) tetrazole (MTet) were synthesized, and their thermal, electrochemical and proton conducting properties were explored. 5-(methacrylamido) tetrazole (MTet) was copolymerized with 4-vinyl benzene boronic acid (VBBA) via conventional free radical copolymerization. The obtained copolymers, P(VBBA-co-MTet), were then doped with phosphoric acid (PA) to produce inorganic–organic hybrid proton conducting membranes. Structural analyses were carried out by Fourier Transform Infrared Spectroscopy (FTIR) and 1H-NMR (Nuclear Magnetic Resonance). The composition of the copolymers was determined by elemental analysis. Thermogravimetric Analysis (TGA) confirmed that the samples were thermally stable up to approximately 170 °C. The surface morphology was characterized by Scanning Electron Microscopy (SEM). Cyclic voltammetry (CV) results demonstrated that the oxidative stability of the samples is 3 V. In the absence of humidity, P(VBBA-co-MTet)-2H3PO4 (S3-2H3PO4) has a maximum proton conductivity of 0.021 Scm−1 at 150 °C. This value was higher than those of previously reported acid doped P(VBBA-co-VIm) and P(VBBA-co-VTri) membranes. Formation of highly conductive, flexible and insoluble free standing films indicates that the matrix has a potential to be used in proton exchange membrane fuel cells (PEMFC).

Photocatalytic activity of vinylidene fluoride-containing copolymers/anatase titanium oxide/silica nanocomposites

A series of three fluorinated copolymers (FP) based on vinylidene fluoride (VDF) were involved in the preparation of original FP/anatase titanium oxide (an-TiO2), and FP/silica/an-TiO2 nanocomposites. These FP copolymers were prepared by conventional free radical copolymerization of VDF with various functional fluorinated comonomers such as F2CCFCO2Me, FCHCFCO2H, and F2CCFC3H6OCOCH3 in good yields (>60%) and had number average molecular weights of ca. 50,000gmol−1. Anatase titanium oxide in the FP/an-TiO2 nanocomposites underwent an effective modification into rutile polymorphism after calcination at 1000°C. Although the parent an-TiO2 nanoparticles changed completely into rutile nanoparticles after calcination at 1000°C, an-TiO2 embedded in the FPs/silica/an-TiO2 nanocomposites retained their structures without any phase transformation into rutile, due to locking the TiO species at the interface of TiO2 domains by the TiOSi units, whose lattice can be formed by the interaction of silica with an-TiO2 nanoparticles. Even after such a thermal treatment, these nanocomposites displayed a higher photocatalytic activity for the discoloration of methylene blue as well as those of the corresponding nanocomposites before calcination, although the original an-TiO2 nanoparticles could not exhibit a photocatalytic ability after calcination. Among these nanocomposites based on VDF-containing copolymers, poly(VDF-co-CF2CFCO2CH3)/SiO2/an-TiO2 before and after calcination displayed better photocatalytic properties than those of the other FP nanocomposites. More interestingly, this FP/silica/an-TiO2 nanocomposite even after calcination at 1000°C was able to preserve the same photocatalytic activity as that before calcination. In addition, these FP/TiO2 and FP/SiO2/TiO2 composites exhibited high thermal stability up to 800°C with a loss weight of 2% (or ca. 14% for the acidic FP) only.

Preparation of Thin Films from New Azolic Copolymers and Investigation of Their Membrane Properties

The preparation and thermal, morphological, electrochemical and proton conducting properties analysis of new azolic copolymers based on 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and 5-(methacrylamido)tetrazole) (MTet) were performed throughout this work. MTet monomer, prepared by the reaction of methacryloyl chloride with 5-aminotetrazole, was copolymerized with AMPS via conventional free radical copolymerization at different monomer feed ratios to achieve poly(MTet-co-AMPS) copolymer membranes. The obtained copolymer membranes were analyzed by FTIR, 1H-NMR, thermogravimetric analysis (TGA), differantial scanning calorimetry (DSC), Elemental Analysis (EA), Cyclic Voltammetry (CV), and Impedance Spectroscopy. The composition of copolymers was determined via elemental analysis (EA). TGA demonstrated that the copolymer electrolyte membranes are thermally stable up to approximately 250°C. The appearance of a single Tg in the DSC curves verified the homogeneity of the membranes. CV curves demonstrated the oxidative stability of the samples in 3 V region. The methanol permeabilities of S1, S2 and S3 copolymers were determined as 1.60×10−9 mol cm−2 s−1, 2.71×10−9 mol cm−2 s−1 and 3.32×10−9 mol cm−2 s−1, respectively, which were comparable with that of Nafion 112 (1.89×10−9 mol cm−2 s−1). In the anhydrous conditions, the maximum proton conductivity was determined as 0.009 Scm−1 at 150°C for poly(MTet-co-AMPS) (S3). The proton conductivity and methanol permeability of poly(MTet-co-AMPS) copolymer membranes increased gradually with the increase of AMPS content. These results suggested that the poly(MTet-co-AMPS) copolymer membranes were particularly promising to be used as proton exchange membranes in PEMFCs.

5-(methacrylamido)tetrazole and vinyl triazole based copolymers as novel anhydrous proton conducting membranes

Polymer electrolytes that have ability to conduct protons at high temperatures have become crucial as the membranes for proton exchange membrane fuel cells (PEMFC) in anhydrous systems. In this work, a novel copolymer based on 5-(methacrylamido)tetrazole (MTet) and vinyl triazole (VTri) was prepared by conventional free-radical copolymerization at several monomer feed ratios to attain poly(VTri-co-MTet) copolymers. The copolymer samples were doped with H3PO4 at several stoichiometric ratios to obtain proton conductive copolymer electrolytes. The obtained membranes were analyzed by FTIR, 1H-NMR, Thermogravimetric Analysis (TGA), Differantial Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Cyclic Voltammetry (CV), and Impedance Spectroscopy. The compositions and molecular weights of copolymers were determined via 1H-NMR analysis. TGA demonstrated that the copolymers are thermally stable up to approximately 220 °C. DSC results illustrated both the homogeneity of the materials by the appearance of a single Tg and the plasticizing effect of the dopant. SEM analysis provided further evidence for the homogeneity of the membranes. CV results demonstrated that the stability window of P(VTri-co-MTet) is 3 V. The copolymer electrolytes, P(VTri-co-MTet)2:1 X = 2, P(VTri-co-MTet)1:1 X = 2, and P(VTri-co-MTet)1:2 X = 2 showed maximum proton conductivities of 0.012 Scm−1, 0.014 Scm−1 and 0.016 Scm−1, respectively, at 150 °C and anhydrous conditions.

Unusual solution phase transition trend of poly(N-isopropylacrylamide-co-bis(N-hydroxyisopropyl pyrrolidone) 2-vinylterephthalate)

A series of water-soluble thermoresponsive copolymers, i.e., poly[(N-isopropylacrylamide-co-bis(N-hydroxyisopropyl pyrrolidone) 2-vinylterephthalate] [P(NIPAm-co-HIPPVTA)], with well-defined comonomer content have been synthesized via conventional free-radical copolymerization at low conversion. The liquid crystalline behavior of the copolymers was investigated using polarized light microscope and differential scanning calorimetry. The results revealed that the P(NIPAm-co-HIPPVTA) exhibit liquid crystallinity when the NIPAm content is lower than 52.2 mol%, which was obviously different from that of previous papers. In addition, thermo-responsive behaviors of copolymer also demonstrated by dynamic light scattering. The cloud points of these copolymers can be tuned over a broad range (i.e., 9.9–81.2 °C) by simply altering the molar content of the HIPPVTA. It is noted that the cloud point of the copolymers showed unexpected trend (i.e., parabolicaly other than linearly or exponentially) with the increasing of HIPPVTA content. That is, with an increase of HIPPVTA molar content, the cloud point of copolymer decreases at first and then increases.

Synthesis and characterization of PSt-b-PVAc diblock copolymers via combination of atom transfer radical polymerization and cobalt-mediated radical polymerization

Atom transfer radical polymerization (ATRP) of styrene (St) initiated with trichloromethyl-terminated poly(vinyl acetate) was performed in the presence of CuCl/PMDETA as a catalyst system at 60 °C. PVAc-CCl3 telomers prepared from radical telomerization (without catalyst) and controlled radical telomerization (in the presence of Co(acac)2/DMF), were used in atom transfer radical polymerization (ATRP) to synthesize polystyrene-b-poly(vinyl acetate) (PSt-b-PVAc) diblock copolymers. The PVAc based block copolymers revealed a significant effect of Co(acac)2/DMF on PVAc macroinitiator which was used in the synthesis of highly ordered diblock copolymer on a well-defined microstructure. Diblock copolymers were characterized by 1H-NMR, DSC and GPC techniques. Reactivity ratios of St and VAc were calculated by the Mayo-Lewis (rSt = 0.563, rVAc = 0.081), Kelen-Todous (rSt = 0.583, rVAc = 0.074) and Finemann-Rose(rSt = 0.569, rVAc = 0.090) methods, which are in a good agreement with those reported for the conventional free-radical copolymerization of St and VAc. The number average molecular weights calculated from 1HNMR spectra were in good agreement with theoretically calculated values for block copolymers.