Preparation Of Copolymers Research Articles

Micellar nanoparticles with tuneable morphologies through interactions between nucleobase-containing synthetic polymers in aqueous solution

Herein, we report the preparation of nucleobase-containing synthetic amphiphilic diblock copolymers using RAFT polymerization.

Electroconducting materials based on polypyrrole

Polypyrrole, along with polyacetylene, polyparaphenylene polyaniline, polythiophene and other polymers structured by conjugated double bonds, is considered as one of the most attractive conducting materials for various applications, such rechargeable batteries, supercapacitors, sensors, gas membranes, magnetic shields, etc. Regarding their biocompatibility and biodegradability in addition to the possibility of controlling their porosity, as well as incorporation of different biological species, and latter by stimulation (e.g. applying electrical field) to control the release of these moieties from polymer matrix, make these polymers suitable for preparation of drug delivery systems, as well as tissue engineering applications. On the other hand, problems concerning poor mechanical properties and environmental instability could be compensated by preparation of blends, copolymers or composite materials. Systems including two components, e.g. conjugated polymers and carbons, supplement the two diverse electrochemical behaviors of both. Lately, composites of polypyrrole, with pseudocapacitance properties and/or carbons (activated carbon, carbon nanotubes) showing double layer capacitance, have been reported in the literature. So, we have made an effort to outline some of most significant results published.

Poly(3-hexylthiophene) End-Functionalization via Quenching Resulting in Heteroatom-Bond Formation

End-functionalized poly(3-hexylthiophene) (P3HT) has contributed to continued advancements in conjugated polymer applications, especially within organic electronics. P3HT synthesized using Kumada catalyst-transfer polymerization (KCTP) has many favourable attributes such as controlled molecular weight, high regioregularity, and narrow dispersity. With the addition of reactive end-groups, P3HT plays an important role in advancing the development of hybrid materials and preparation of block copolymers. Exploring methods of end-functionalization that result in heteroatom-bond formation, giving a non-carbon atom bonded to the terminal thiophene, could help control and understand the p–n junction of hybrid materials. This research highlight focuses on the development of a novel and facile way of end-functionalizing P3HT with chalcogens.

Characterization and Preparation of PEG-Polyimide Copolymer Asymmetric Flat Sheet Membranes for Carbon Dioxide Separation

Characterization and Preparation of PEG-Polyimide Copolymer Asymmetric Flat Sheet Membranes for Carbon Dioxide Separation

Preparation of tourmaline-containing functional copolymer p(TUC/BA/MMA) and its performances

ABSTRACTIn order to develop the tourmaline-containing functional polymer, the double-bond-containing undecenoyl group was introduced onto the surface of tourmaline to synthesize a polymerizable organic tourmaline undecylenate (TUC) by the surface modification of tourmaline with 10-undecenoyl chloride. The TUC was then copolymerized with butyl acrylate (BA) and methyl methacrylate (MMA) to obtain the tourmaline-containing functional copolymer p(TUC/BA/MMA), which showed an excellent storage stability. The structures of TUC and its copolymers were characterized by means of IR, XRD, SEM, and EDX. The results indicated that the tourmaline-containing functional copolymer displayed excellent mechanical, far-infrared radiating, and negative ion releasing performances.

Light‐Controlled Radical Polymerization of Functional Methacrylates Prepared by Enzymatic Transacylation

Well‐defined homo and block copolymers are prepared with methyl methacrylate, pentyl methacrylate, 3‐phenylpropyl methacrylate, and 6‐thiobenzoylhexyl methacrylate using Ir(ppy)3 as a catalyst. It is shown that the advantages of the light‐controlled radical polymerization can be exploited also for these special monomers as prepared by enzymatic transacylation without time‐consuming labor‐intensive removal of side products. Furthermore, it is shown that the polymerization is significantly affected even by small variations in the irradiation and therefore also by choice of the light source. In contrast to our recent report we therefore recommend removal of the heterogeneous supported enzyme by filtration before polymerization. Because of the sensitivity of the polymerization process to the irradiation, turbidity caused by the bead‐supported enzyme can affect the reproducibility of the polymer preparation. Results obtained with methyl methacrylate as monomer could only be transferred to the above‐mentioned functional monomers by proper choice of the light source. On the basis of kinetic investigations, the effect of the irradiation source, the catalyst concentration, and the alcohol residue on the methacrylate used are discussed. Finally, the optimized experimental conditions are applied for the preparation of different block copolymers. image

Clickable Nucleic Acids: Sequence‐Controlled Periodic Copolymer/Oligomer Synthesis by Orthogonal Thiol‐X Reactions

AbstractSynthetic polymer approaches generally lack the ability to control the primary sequence, with sequence control referred to as the holy grail. Two click chemistry reactions were now combined to form nucleobase‐containing sequence‐controlled polymers in simple polymerization reactions. Two distinct approaches are used to form these click nucleic acid (CNA) polymers. These approaches employ thiol–ene and thiol‐Michael reactions to form homopolymers of a single nucleobase (e.g., poly(A)n) or homopolymers of specific repeating nucleobase sequences (e.g., poly(ATC)n). Furthermore, the incorporation of monofunctional thiol‐terminated polymers into the polymerization system enables the preparation of multiblock copolymers in a single reaction vessel; the length of the diblock copolymer can be tuned by the stoichiometric ratio and/or the monomer functionality. These polymers are also used for organogel formation where complementary CNA‐based polymers form reversible crosslinks.

Clickable Nucleic Acids: Sequence-Controlled Periodic Copolymer/Oligomer Synthesis by Orthogonal Thiol-X Reactions.

Synthetic polymer approaches generally lack the ability to control the primary sequence, with sequence control referred to as the holy grail. Two click chemistry reactions were now combined to form nucleobase-containing sequence-controlled polymers in simple polymerization reactions. Two distinct approaches are used to form these click nucleic acid (CNA) polymers. These approaches employ thiol-ene and thiol-Michael reactions to form homopolymers of a single nucleobase (e.g., poly(A)n ) or homopolymers of specific repeating nucleobase sequences (e.g., poly(ATC)n). Furthermore, the incorporation of monofunctional thiol-terminated polymers into the polymerization system enables the preparation of multiblock copolymers in a single reaction vessel; the length of the diblock copolymer can be tuned by the stoichiometric ratio and/or the monomer functionality. These polymers are also used for organogel formation where complementary CNA-based polymers form reversible crosslinks.

Aqueous RAFT Polymerization of Imidazolium-Type Ionic Liquid Monomers: En Route to Poly(ionic liquid)-Based Nanoparticles through RAFT Polymerization-Induced Self-Assembly.

The synthesis by aqueous RAFT polymerization of hydrophilic narrowly dispersed imidazolium-based poly(ionic liquid)s (Đ typically below 1.20) is reported. Full monomer conversion is achieved within hours and high end-group fidelity of the living end groups affords the preparation of well-defined block copolymers. The resulting poly(ionic liquid) macroRAFT agents are finally exploited to polymerize 2-vinylpyridine in water and generate PIL-based nanoparticles of various morphologies (spheres, vesicles, or worms) in a one-pot surfactant-free process.

Anti-Bioadhesive Coating Based on Easy to Make Pseudozwitterionic RAFT Block Copolymers for Blood-Contacting Applications.

Amphiphilic diblock copolymer containing randomly distributed positive and negative charged monomers are synthesized using RAFT polymerization technique to be used as anti-bioadhesion coatings for hydrophobic surfaces. Quaternized 2-(dimethylamino) ethyl methacrylate and potassium 3-sulfopropyl methacrylate (P[qDMAEMA-co-KSPMA]) are randomly polymerized to yield an anti-bioadhesion block which is, in one pot, copolymerized with styrene as an anchoring block. This copolymer has demonstrated high anti-bioadhesion properties to avoid the blood clotting in medical devices through a simple and facile approach to preparation of pseudozwitterionic copolymers.

Radiation-induced graft polymerization of chitosan onto poly(3-hydroxybutyrate)

Chitosan is among the most studied biopolymers and offers important advantages, such as biodegradability, biocompatibility and nontoxicity. In this study, this polysaccharide was grafted onto poly(3-hydroxybutyrate) using the simultaneous gamma-irradiation-initiated polymerization method. The polyester was immersed in diverse solvents, which allowed the preparation of graft copolymers with different yields and crystallinities. A successful synthesis and the estimation of the degree of crystallinity were verified by spectroscopic and calorimetric techniques. The most suitable method was found to be the thermoanalytical approach because it displayed a linear relationship between the degree of crystallinity and the increasing degree of grafting. The results also indicated that the lowest degree of grafting was seen for acetic acid (14.27%), while the highest degree corresponded to ethyl acetate (32.11%). The mechanism of grafting was proposed on the basis of the experimental results.

Visible Light-Controlled Radical Polymerization of Propargyl Methacrylate Activated by a Photoredox Catalyst fac-[Ir(ppy)3

Despite the robustness and flexibility of thermal controlled radical polymerization (CRP), it still remains a big challenge to prepare clickable polymers bearing acetenyl groups. In this paper, visible light CRP of propargyl methacrylate (PgMA) is investigated using ethyl-α-bromophenylacetate as initiator and fac-Ir(ppy)3 as a photoredox catalyst. By controlling the polymerization time, a linear increase of Mn with monomer conversion and narrow polydispersity index is achieved. Specifically, with [PgMA]/[Initiator]/[fac-Ir(ppy)3]=210:1:0.0285, the products show Mn=8300 g/mol and Mw/Mn=1.24 at 17% monomer conversion and Mn=17100 g/mol and Mw/Mn=1.52 at 50% monomer conversion. This result is much better than that of thermally activated Cu-ATRP of PgMA. When the ratio of MMA/PgMA is 5:1, the copolymerization product shows Mn=25300 g/mol and Mw/Mn=1.75 at 66% monomer conversion. The FTIR, 1H-NMR and 13C-NMR spectra of the PPgMA show no sp2-sp2 carbon-carbon bond, indicating that acetenyl groups are intact. In conclusion, this technology offers a versatile route for the preparation of (co)polymers with pendant alkynyl groups.

Preparation of Fluorosilicone Random Copolymers with Properties Superior to Those of Fluorosilicone/Silicone Polymer Blends

Copolymers of poly(dimethylsiloxane-methyltrifluoropropylsiloxane-methylvinylsiloxane) (P(DMS-MTFPS-MVS) or PDFV) were prepared by co-polycondensation of dimethylsiloxanediol, methyltrifluoropropylsiloxanediol and methylvinyldiethoxysilane using potassium silanolate as a catalyst. The characterization results obtained from gel permeation chromatography, 1H NMR spectroscopy, 29Si NMR spectroscopy and dynamic mechanical analysis indicated that PDFV copolymers possessed a higher molecular weight and exhibited a more uniform distribution of methyltrifluoropropylsiloxane (MTFPS) units along the polymer chain than the copolymers prepared by ring-opening copolymerization. The solubility parameters (δ) of PDMS, PMTFPS and PDFV were determined by measuring the maximum degree of swelling (Qmax) in solvents with different δ values. The mechanical property, phase structure and oil resistance of PDFV copolymers and PDMS/PMTFPS blends were compared. The results indicated that the PDMS/PMTFPS blends exhibited serious phase separation, leading to a pronounced drop in the tensile strength. However, the homogeneous PDFV compounds with various amounts of the MTFPS unit exhibited good mechanical properties. In addition, the copolymers exhibited much better oil resistance than the blends did in engine oil and IRM 903 test oil. However, the blends exhibited better fuel resistance than the copolymers when the amount of the MTFPS unit was less than a certain value related to the δ of the fuel.

Preparation of copolymers of acrylic acid and 3-methacryloxypropyl-trimethoxysilane by the method of emulsion copolymerization

The method for preparing silicone acryl polymer by emulsion copolymerization of acrylic acid and 3-methacryloxypropyl-trimethoxysilane with a reaction initiator (ammonium persulfate) is presented in the article on the basis of experimental studies. The optimum conditions of synthesis are determined. Based on the study of the kinetics of the reaction by gravimetric copolymerization method, it was found that it is desirable to conduct the reaction for 4,5 hours at 90 o C, since after this time yield of copolymer was 53,3 %. During synthesis it is obtained silicone acryl polymer that is a viscous transparent liquid without sharp odor, soluble in organic solvents. The properties of the silicone acryl polymer are investigated and characterized: molecular mass is calculated, determined the composition of the copolymer is determined and IR spectral analysis is conducted. This polymer is suitable for use in paints and varnishes as a surface modifier.

Low glass transition temperature poly(ionic liquid) prepared from a new quaternary ammonium cationic monomer

Well‐defined poly(ionic liquid)s (PILs) were synthesized by normal and activators regenerated by electron transfer atom transfer radical polymerization (ATRP) using a new ionic liquid monomer, N‐(4‐vinylbenzyl)‐tris[2‐(2‐methoxyethoxy)ethyl]ammonium bis(trifluoromethylsulfonyl)imide (VBTA+Tf2N−). ATRP was also used for the preparation of PIL block copolymers using di‐functional PIL macroinitiators. Differential scanning calorimetry measurement showed the polyVBTA+Tf2N− had a rather low glass transition temperature of −43°C. Copyright © 2015 John Wiley & Sons, Ltd.

Synthesis of β-cyclodextrin-Based Star Block Copolymers with Thermo-Responsive Behavior

Star polymers are one example of three-dimensional macromolecules containing several arms with similar molecular weight connected to a central core. Due to their compact structure and their enhanced segment density in comparison to linear polymers of the same molecular weight, they have attracted significant attention during recent years. The preparation of block-arm star copolymers with a permanently hydrophilic block and an “environmentally” sensitive block, which can change its nature from hydrophilic to hydrophobic, leads to nanometer-sized responsive materials with unique properties. These polymers are able to undergo a conformational change or phase transition as a reply to an external stimulus resulting in the formation of core–shell nanoparticles, which further tend to aggregate. Star-shaped copolymers with different cores were synthesized via atom transfer radical polymerization (ATRP). The core-first method chosen as synthetic strategy allows good control over the polymer architecture. First of all the multifunctional initiators were prepared by esterification reaction of the hydroxyl groups with 2-chloropropionyl chloride. Using β-cyclodextrin as core molecules, which possess a well-defined number of functional groups up to 21, allows defining the number of arms per star polymer. In order to prepare stimuli-responsive multi-arm copolymers, containing a stimuli-responsive (poly(N-isopropylacrylamide) (PNIPAAm)) and a non-responsive block (poly(N,N-dimethylacrylamide) (PDMAAm)), consecutive ATRP was carried out. The polymers were characterized intensively using NMR spectroscopy and size exclusion chromatography (SEC), whereas the temperature-depending aggregation behavior in aqueous solution was determined via turbidimetry and differential scanning calorimetry (DSC).

Preparation of cellulose graft copolymer based on the combination of ionic liquids and microwave heating

Cellulose is a promising raw material that can be modified through a variety of chemical modifications to obtain many functional materials. Cellulose-g-acrylamide copolymer was prepared in a homogeneous medium by using N,Nʹ-methylenebisacrylamide as the crosslinker without any radical initiator using microwave radiation. The 1-butyl-3-methylimidazolium chloride ionic liquid, which is an environmentally friendly and effective reaction medium, was chosen to dissolve the cellulose and the homogeneous graft polymerisation of acrylamide onto the cellulose. Owing to the effects of microwave heating, the reaction time was significantly shortened: 1 minute microwave heating was adequate, compared to 30 minutes to 5 hours with a conventional heating method. The influences of monomer concentration, crosslinker dosage, microwave power and reaction time were investigated. The obtained cellulose graft copolymer was characterised by infrared spectrum, thermogravimetric analysis and scanning electron microscopy. A feasible reaction mechanism of grafting based on microwave heating was proposed.

Visible-Light-Controlled Living Radical Polymerization from a Trithiocarbonate Iniferter Mediated by an Organic Photoredox Catalyst

Living radical polymerization of acrylates and acrylamides from trithiocarbonate iniferters using a compact fluorescent lamp (CFL) bulb and 10-phenylphenothiazine as an organic photoredox catalyst is reported. With this system, chain growth can be efficiently switched between "on" and "off" in response to visible light. Polymer molar masses increase linearly with conversion, and narrow molar mass distributions are obtained. The excellent fidelity of the trithiocarbonate-iniferter enables the preparation of triblock copolymers from macro-iniferters under the same visible-light mediated protocol, using UV light without a photoredox catalyst or under traditional thermally induced RAFT conditions. We expect that the simplicity and efficiency of this metal-free, visible-light-mediated polymerization will enable the synthesis and modification of a range of materials under mild conditions.

Access to Amphiphilic Cis-Configurated Polyamide-3 Using Alcohols as Initiators

The synthesis of polyamide-3 from 4a,5,8,8a-tetrahydro-1H-benzo[d][1,3]oxazine-2,4-dione (β-NCA, 1) using methanol, dye (Disperse Red 13), and poly(ethylene glycol) as initiator is described. The ring-opening polymerization under release of CO2 produces polyamides-3 with definite terminal groups, high purity, and relatively narrow dispersity. This route was used for preparation of block copolymers from as an example.

Dual functionalized telechelic block copolymers with reproducible block sizes prepared by microwave assisted RAFT polymerization

This work demonstrates the preparation of amphiphilic block copolymers with remarkable reproducibility of each block and the dual functionalization of the chain ends with a targeting unit and a fluorescent moiety. The size of the resulting micelles can be controlled between 17 and 55 nm by tuning the size of the hydrophobic block. The polymerization of the diblock was carried out by microwave assisted reversible addition fragmentation chain transfer (RAFT) polymerization and results in a very high degree of reproducibility of the number of repeat units of each block. The hydrophilic block of the polymer comprised of poly(2-hydroxyethyl acrylate) (pHEA) while the hydrophobic block was made of poly(2-ethylhexyl acrylate) (pEHA). Folic acid, a folate receptor targeting moiety, was tethered to the α end of the polymer while anthracene was covalently linked to the ω end. The ω end covalent attachment is via a redox cleavable disulfide bond, which is optimal for controlled drug delivery systems. High efficiencies of α- and ω-conjugations were obtained as determined by UV and NMR measurements.