Method For Synthesis Of Polymers Research Articles

Macromolecular design and application using Mn2(CO)10‐based visible light photoinitiating systems

AbstractThe environmentally friendly Mn2(CO)10‐based visible light photoinitiating system is a powerful method for the preparation of linear and crosslinked polymeric structures. From a practical point of view, the most important feature of this initiating system is its optical characteristics in the visible range with high quantum yield and good solubility properties. This photoinitiating system is applicable for a variety of monomers that can be polymerized via either radical or cationic mechanisms. Various complex macromolecular structures such as telechelic polymers, block and graft copolymers, polymer networks and surface modifications can be simply prepared by using halogenated precursors. This photoinitiating system is also combined with controlled radical polymerization techniques providing a mild and efficient method for polymer synthesis. © 2016 Society of Chemical Industry

ChemInform Abstract: Precipitation Polymerization: A Versatile Tool for Preparing Molecularly Imprinted Polymer Beads for Chromatography Applications

AbstractReview: 116 refs.

Organocatalyzed atom transfer radical polymerization driven by visible light.

Atom transfer radical polymerization (ATRP) has become one of the most implemented methods for polymer synthesis, owing to impressive control over polymer composition and associated properties. However, contamination of the polymer by the metal catalyst remains a major limitation. Organic ATRP photoredox catalysts have been sought to address this difficult challenge but have not achieved the precision performance of metal catalysts. Here, we introduce diaryl dihydrophenazines, identified through computationally directed discovery, as a class of strongly reducing photoredox catalysts. These catalysts achieve high initiator efficiencies through activation by visible light to synthesize polymers with tunable molecular weights and low dispersities.

A framework for accurate evaluation of the promise of aquaporin based biomimetic membranes

Aquaporin based membranes (ABMs) are considered a promising biomimetic desalination technology and have been intensively studied over the last few years. The most common strategy to synthesize ABMs is to deposit the aquaporin incorporated lipid or block copolymer (BCP) vesicles onto porous substrates or more recently to integrate them within the active layer of polyamide membranes. However, ABMs with orders of magnitude improvement in permeability and perfect salt rejections proposed in initial work have not been realized. Early results were based on materials and methods that were rudimentary, especially considering the progress that has been made in this field. In particular, low signal to noise ratios (SNRs <50) of stopped flow measurements for vesicle-based assays have led to large inaccuracies in permeability estimation. We show that such low SNRs can result from using vesicle samples with a high concentration of micelles and provide a connection between morphology and data quality. We have conducted a comprehensive evaluation of the true promise of these membranes using improved methods for polymer synthesis, self-assembly, experimental evaluation as well as calculations that more directly compare the outcome of biophysical evaluations to those used in the desalination membrane industry. We propose these as standard methods for use in ABM research. The role of concentration polarization in introducing error into vesicle based permeability measurements is identified. We further describe a simple technique to calculate the expected flux from a membrane synthesized using vesicle immobilization on a permeable substrate that can be used to estimate realistic membrane fluxes from stopped flow data. These calculations show that it is possible to achieve permeabilities one to two orders of magnitude higher than current membranes using ABMs but several innovations will be needed to reach this potential.

Optimization of long-range order in solvent vapor annealed poly(styrene)-block-poly(lactide) thin films for nanolithography.

Detailed experiments designed to optimize and understand the solvent vapor annealing of cylinder-forming poly(styrene)-block-poly(lactide) thin films for nanolithographic applications are reported. By combining climate-controlled solvent vapor annealing (including in situ probes of solvent concentration) with comparative small-angle X-ray scattering studies of solvent-swollen bulk polymers of identical composition, it is concluded that a narrow window of optimal solvent concentration occurs just on the ordered side of the order-disorder transition. In this window, the lateral correlation length of the hexagonally close-packed ordering, the defect density, and the cylinder orientation are simultaneously optimized, resulting in single-crystal-like ordering over 10 μm scales. The influences of polymer synthesis method, composition, molar mass, solvent vapor pressure, evaporation rate, and film thickness have all been assessed, confirming the generality of this behavior. Analogies to thermal annealing of elemental solids, in combination with an understanding of the effects of process parameters on annealing conditions, enable qualitative understanding of many of the key results and underscore the likely generality of the main conclusions. Pattern transfer via a Damascene-type approach verified the applicability for high-fidelity nanolithography, yielding large-area metal nanodot arrays with center-to-center spacing of 38 nm (diameter 19 nm). Finally, the predictive power of our findings was demonstrated by using small-angle X-ray scattering to predict optimal solvent annealing conditions for poly(styrene)-block-poly(lactide) films of low molar mass (18 kg mol(-1)). High-quality templates with cylinder center-to-center spacing of only 18 nm (diameter of 10 nm) were obtained. These comprehensive results have clear and important implications for optimization of pattern transfer templates and significantly advance the understanding of self-assembly in block copolymer thin films.

The effect of RAFT-derived cationic block copolymer structure on gene silencing efficiency

In this work a series of ABA tri-block copolymers was prepared from oligo(ethylene glycol) methyl ether methacrylate (OEGMA475) and N,N-dimethylaminoethyl methacrylate (DMAEMA) to investigate the effect of polymer composition on cell viability, siRNA uptake, serum stability and gene silencing. Reversible Addition–Fragmentation Chain Transfer (RAFT) polymerization was used as the method of polymer synthesis as this technique allows the preparation of well-defined block copolymers with low polydispersity. Eight block copolymers were prepared by systematically varying the central cationic block (DMAEMA) length from 38 to 192 monomer units and the outer hydrophilic block (OEGMA475) from 7 to 69 units. The polymers were characterized using size exclusion chromatography and 1H NMR. Chinese Hamster Ovary-GFP and Human Embryonic Kidney 293 cells were used to assay cell viability while the efficiency of block copolymers to complex with siRNA was evaluated by agarose gel electrophoresis. The ability of the polymer–siRNA complexes to enter into cells and to silence the targeted reporter gene enhanced green fluorescent protein (EGFP) was measured by using a CHO-GFP silencing assay. The length of the central cationic block appears to be the key structural parameter that has a significant effect on cell viability and gene silencing efficiency with block lengths of 110–120 monomer units being the optimum. The ABA block copolymer architecture is also critical with the outer hydrophilic blocks contributing to serum stability and overall efficiency of the polymer as a delivery system.

New methods of polymer synthesis

New methods of polymer synthesis

Surface Morphological Changes in Monolayers of Aromatic Polyamides Containing Various N-Alkyl Side Chains

We synthesized new aromatic polyamides (poly-(N-alkylated benzamides), abbrev. PABA(n)) having both a rigid main chain and a flexible side chain with different lengths. We investigated the solid-state structures, that is, the molecular orientation and surface morphology, of organized molecular films of PABA(n) by performing surface pressure-area (pi-A) isotherm, in-plane and out-of plane X-ray diffraction (XRD), polarized infrared spectroscopy, and atomic force microscopy (AFM) measurements. The solid-state structure of poly-(N-methyl benzamide) (PABA(1)) belonged to the monoclinic system, whereas PABA(3), PABA(4), and PABA(5) showed an orthorhombic packing pattern. PABA(7) and PABA(8) formed amorphous polymers. In the case of PABA(17), a two-dimensional hexagonal lattice was formed as a subcell consisting of side chains. These polymer monolayers were highly condensed on a water surface at 15 degrees C. Out-of-plane XRD measurement results showed that the PABA(1), PABA(3), PABA(4), and PABA(5) multilayers showed large periodicities of 50-60 A. From AFM observation results, it was found that these aromatic polyamides formed single particle layers of hydrophilic groups localized at the bottom of the particles. On the other hand, PABA(7) and PABA(8) monolayers showed irregularity and exhibited shapeless morphologies. In addition, an organized molecular film of PABA(17) formed a highly ordered layer structure (periodicity of 30 A) and a giant circular domain (diameter of 20 nm) made of a side chain crystal. The PABA(17) monolayer showed a hexagonal packing pattern formed due to van der Waals interaction between the flexible side chains. From these experimental findings, it was concluded that the polymer synthesis method employed in the present study can be directly used to control the crystal structure (the third order structure of polymers), molecular arrangement, and surface morphologies of polymer monolayers.

Solid-state Structure and Formation of Organized Molecular Films for Poly-(&lt;i&gt;N&lt;/i&gt;-alkylated benzamides) Containing Various Chain Lengths

We investigated the solid-state structure and formation of organized molecular films for newly synthesized aromatic polyamides having both a rigid main-chain and a flexible side-chain with different lengths by wide angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), and surface pressure-area (π–A) isotherm measurements. The solid-state structure of poly-(N-methylbenzamide) (PABA1) belonged to the monoclinic system, whereas PABA3, PABA4, and PABA5 showed an orthorhombic packing system. PABA7 and PABA8 formed amorphous polymers. In the case of PABA17, a two-dimensional hexagonal lattice was formed as a sub-cell consisting of side chains. These polymer monolayers were highly condensed on a water surface at 15 °C. From these experimental findings, it is concluded that the polymer synthesis method employed in this study can be directly used to control the crystalline morphology (the third order structure of polymers) of polymer monolayers.

Bacterial Production of Poly(3-hydroxybutyrate). An Undergraduate Student Laboratory Experiment

As part of a multidisciplinary course that is cross-listed between five departments, we developed an undergraduate student laboratory experiment for culturing, isolating, and purifying the biopolymer, poly(3-hydroxybutyrate), PHB. This biopolyester accumulates in the cytoplasm of bacterial cells under specific growth conditions, and it has attracted much recent interest since its biodegradability makes it environmentally friendly and its biocompatibility makes it an attractive choice for medical and therapeutic applications. This laboratory experiment would be a valuable addition to any traditional chemistry or polymer science curriculum, since it exposes the student to the field of biotechnology and teaches biological methodologies that are different from traditional methods of polymer synthesis. The experiment is designed so that the students perform the PHB cultivation and extraction processes in three stages that are easily accommodated within the scheduling confines of a typical undergraduate laboratory course. Moreover, the bacterially produced PHB can then be used by students in subsequent exercises for comparison with polymers produced using chemical synthesis. In addition to chemistry and polymer science curricula, this laboratory experiment would also be suitable for a variety of biology, biochemistry, or biotechnology curricula.

Polymers with dihydroxy/dialkoxybenzene moieties

Polymers with dialkoxybenzene and dihydroxybenzene units are countless and their applications are nowadays widespread. The reputed methods of polymer synthesis and the newly emerged ones have been employed to make these special polymers. Apart from these methods, the dialkoxy/dihydroxybenzene-bearing polymers have also been prepared via electrolytic and enzymatic routes or via an indirect one such as the functionalization by attachment. The dialkoxy/dihydroxy entities were found to bring about either an enhancement of the existing properties of the polymers or merely novel ones. Metallic adsorption, redox activity, adhesion-promoting, and lacquer coating ability of the polymer were ensured by the dihydroxybenzene moiety, whereas the dialkoxybenzene one imparted an increase in the electrical conductivity and electroluminescence of the poly(para-phenylene)s (PPPs) and the poly(phenylenevinylene)s (PPVs) and their related properties.

Morphology of the surface layer of polymers modified by gaseous fluorine

A change in the surface structure of low-density polyethylene films upon chemical modification by gaseous fluorine has been studied by scanning electron microcopy and X-ray spectral analysis. It has been demonstrated that this treatment leads to formation of the wavy surface; its characteristics depend on the method of polymer synthesis and the initial structure of the test sample. A possible mechanism for structural changes in the surface layer of the polymer during fluorination is considered. It is suggested that the molar volume and the configuration of polymer macromolecules change in the course of replacement of hydrogen atoms with fluorine atoms. Mathematical modeling has been performed for the formation of the fluorinated layer with due regard for chemical transformations of macromolecules and structural heterogeneity of the polymers. The isosurfaces of the polymer with various degrees of fluorination calculated within the framework of the above model indicate that the fluorinated layer being formed is characterized by unequal thickness due to different rates of fluorine diffusion in amorphous and crystalline regions. It has been shown that the degree of fluorination of the polymer is dependent on the duration of treatment. This relationship is in satisfactory agreement with the previous experimental data.

Microfabrication by X‐ray‐induced polymerization above the lower critical solution temperature

AbstractA polymer synthesis method is presented in which chain growth driven by exothermic reaction stimulates a gradual chain collapse. The globular precipitates in such systems can be restrained from coalescing by polymerizing in a quiescent environment. Time‐resolved small‐angle scattering study of the methacrylic acid polymerization kinetics in a quiescent system above its lower critical solution temperature (LCST) in water reveals the following features of this method: (a) growing oligomers remain as rigid chains until a critical chain length is reached, at which they undergo chain collapse, (b) radius of gyration increases linearly with time until a critical conversion is reached, and (c) radius of gyration remains constant after the critical conversion, even while conversion is gradually increasing. Following this self‐stabilizing growth mechanism, we show that nanoparticles can be directly synthesized by polymerizing N‐isopropylacrylamide above its LCST in water. The average size of nanoparticles obtained from a polymer–solvent system is expected to be the maximum extent of reaction spread at that monomer concentration. This hypothesis was then verified by polymerizing N‐isopropylacrylamide above their LCST in water, but by initiating the reaction with X‐rays shielded by a mask. The microfabricated patterns conform well to the size and shape of the mask used confirming that the growing chains do not propagate beyond the exposed regions as long as the reaction temperature is maintained above the LCST. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 429–425, 2006

Solid-Phase Synthesis of Polymers Using the Ring-Opening Metathesis Polymerization

We report a general method for the solid-phase synthesis of polymers via the ring-opening metathesis polymerization (ROMP). The method involves polymerization in solution to form a block copolymer, immobilization of the polymer via reaction of one block with a resin-bound functional group, modification of the other block, and liberation of the polymer from the resin. We demonstrated the utility of this approach by generating a block copolymer with an N-hydroxysuccinimidyl ester-substituted block (for on-resin functionalization) and a maleimide-substituted block (for conjugation to the resin). We showed that the Diels-Alder reaction can be employed to immobilize the polymers and that amines of diverse structure can be used to modify the resin-bound polymers. The reversibility of the furan-maleimide Diels-Alder adduct was exploited to liberate the polymer from the support. Specifically, treatment of the resin with cyclopentadiene resulted in complete polymer release. The resulting polymers are functional: they were as potent in assays with the lectin concanavalin A as polymers generated by traditional solution routes. We anticipate that this method can be used for the rapid synthesis of diverse polymers via ROMP.

The use of radical polymerization in the synthesis of telechelic oligomers

The following is a review of the newer methods that are available for the synthesis of telechelic oligomers using radical polymerizations. We detail advances in the field since John Ebdon’s review published in 1995 [J.R. Ebdon, Eastmond, New Methods of Polymer Synthesis, Blackie Academic, 1995, ISBN 0751402427]. The available methods are categorized into sections on: chain cleavage techniques; controlled polymerizations; dead end polymerizations and transfer methods. We also introduce a new mathematical technique for determining chain transfer constants that is applicable when transfer to solvent is the dominant termination mechanism. In this new method, we differentiate the Mayo equation with respect to solvent concentration ([ S]) and then plot ∂(1/ X n )/∂[ S] against 1/[ M]. This procedure then gives C s as the gradient.

Recent work on entropically‐driven ring‐opening polymerizations: some potential applications

AbstractThe entropically‐driven ring‐opening polymerization of macrocyclic monomers (&gt;ca. 14 ring atoms per repeat unit) and/or macrocyclic oligomers is a relatively new method of polymer synthesis that exploits the well‐known phenomenon of ring‐chain equilibria. It attracts interest because of its novel features. For example, these ring‐opening polymerizations emit no volatiles and little or no heat. This review considers the principles of entropically‐driven ring‐opening polymerizations, gives selected examples and discusses potential applications. The latter include micromolding, high throughput syntheses and the synthesis of supramolecular polymers. Copyright © 2005 John Wiley &amp; Sons, Ltd.

Active polycondensation: from pep tide chemistry to amino acid based biodegradable polymers

AbstractNew polycondensation (PC) methods of polymer synthesis using non‐traditional active derivative of dicarboxylic acids are reviewed. The new PC methods are named by general name “Active Polycondensation” (APC) to tell them from traditional low‐temperature PC. The most of these methods are based on well known in peptide chemistry approaches to the activation of carboxylic groups. In the present paper the syntheses of heterochain polymers of basic classes ‐ polyamides, polyesters, polyurethanes, polyureas, and polybenzazoles by interaction of various active diesters with di‐ and polyfunctional nucleophiles are discussed in brief. Special attention is given to the synthesis of non‐conventional heterochain macromolecular systems, in particular poly(ester amide)s (PEAs), composed of naturally occurring α‐amino acids and other non‐toxic building blocks like fatty diacids and diols ‐ synthetic analogues of naturally occurring amino acid based polymers ‐ peptides and proteins. The synthesis and properties, biodegradation, and some practical applications of PEAs are discussed in brief.

Editorial announcement

The editors of the Journal of Polymer Science Part A: Polymer Chemistry are delighted to congratulate our fellow editor, Virgil Percec, P. Roy Vagelos Professor of Chemistry at the Department of Chemistry, University of Pennsylvania, as the 2004 recipient of the prestigious ACS Award in Polymer Chemistry sponsored by ExxonMobil Chemical Company. The award will be presented at the 227th ACS National Meeting in Anaheim, CA and cites Virgil for “his contributions to the development of novel methods of polymer synthesis for both covalent and supramolecular systems from liquid-crystalline polymers to dendrimers”. Virgil joins our illustrious Advisory Editors, Professors Jean M. J. Fréchet, Robert H. Grubbs, and David A. Tirrell and founding editor Herman F. Mark as worthy recipients of this important and esteemed award. As a scientist and spokesman for polymer chemistry, Virgil Percec is unique in the international community. Over the last 25 years, Virgil has contributed a body of independent research that is unmatched in originality, breadth, and scope. Beginning from his original work involving the synthesis and chemistry of poly(arylacetylene) sterioisomers, proceeding to metal-catalyzed arylations, phase-transfer catalyzed polymerizations, living and other controlled radical polymerization, and supramolecular polymer chemistry, Virgil has significantly influenced a generation of polymer chemists with his prodigious energy and extraordinary dedication to scholarly work. A number of new and important areas of polymer chemistry have emerged as a result of Virgil's insight, and he has applied his enormous skills creatively to solve real problems of scientific and technological significance. We would like to express our most sincere congratulations to Virgil Percec on this well-deserved award. It is an honor to work with him as editors of the Journal of Polymer Science Part A: Polymer Chemistry and we thank Virgil for his continuing and invaluable contributions to the journal, the success of which is evident from the fifth straight year of an increasing impact factor. The innovations and insights that Virgil brings not only to the journal but to all aspects of polymer chemistry are his trademark and we express our gratitude to him for all of his efforts.

Synthesis of an amylose–polymer inclusion complex by enzymatic polymerization of glucose 1-phosphate catalyzed by phosphorylase enzyme in the presence of polyTHF: a new method for synthesis of polymer–polymer inclusion complexes

The enzymatic polymerization of α-D-glucose 1-phosphate (Glc-1-P) with phosphorylase in the presence of polytetrahydrofuran (polyTHF) leads to an amylose–polyTHF (polymer–polymer) inclusion complex; the present reaction system provides a new method for the preparation of polymer–polymer inclusion complexes.

Polymer Deposition from Supercritical Solutions for Sensing Applications

Polymer surfaces are important in many applications including chemical sensing, corrosion protection, lubrication, and medicine. The growing demand for surfaces with specific and improved properties has catalyzed the development of new methods of polymer synthesis and processing that provide control of surface properties at the micro- and nanometer scales. Rapid expansion of supercritical solutions (RESS) is a technique that takes advantage of the enormous solubility change that occurs in a rapidly expanding supercritical solution in order to form precipitates with narrow and tunable size distributions. We have developed and tested a new RESS apparatus, incorporating a 340 cm3 extraction vessel and a capillary nozzle. The system provides the ability to independently control important expansion parameters including temperature, pressure, solute concentration, and nozzle geometry. Microspheres of high molecular weight poly(dimethylsiloxane) were deposited onto the sensing surface of a microfabricated transducer using the RESS technique. The siloxanes are excellent candidates for chemical sensing applications because of their affinity to particular organic vapors and other advantageous physical properties including low glass transition temperature, low crystallinity, and the potential for chemical modification for enhanced selectivity. The miniature chemical sensor was tested upon exposure to hexane vapor and exhibits a fast, reversible response.