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Polymer Chemistry

Xinpeng Zhang, Sijia Huang, Maciej Podgórski, Xun Han, Mauro Claudino, Christopher N Bowman
We present a thermally initiated thiol-Michael reaction based on initiation via the temperature-dependent thiol-TEMPO oxidation-reduction reaction. In the presence of a thiol, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO, p K a = 5.5) is reduced to produce a much stronger base, i.e., tetramethylpiperidine (TMP, p K a = 11.4) in a temperature dependent process. This oxidation-reduction process is dramatically accelerated at elevated temperature, which allows for thermally controlled initiation of the base-catalyzed thiol-Michael addition reaction and potentially other base-catalyzed reaction systems...
August 28, 2018: Polymer Chemistry
Pengrui Wang, Ji Hoon Park, Mahmoud Sayed, Tae-Sun Chang, Amy Moran, Shaochen Chen, Sang-Hyun Pyo
Bisphenol A, (2,2-bis(4-hydroxyphenyl)propane, BPA)-free polycarbonate (PC) from six-membered di-cyclic carbonate, di-trimethylolpropane di-cyclic carbonate (DTMPC) was developed as a new type of PC by ring opening homo-polymerization. The polymerization was controlled by using metal-free organic-based catalyst systems. The results indicated that the conversion rate depends on the basicity of the catalyst in the order of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 4-dimethylaminopyridine (DMAP), triethylamine (TEA) from high to low...
July 21, 2018: Polymer Chemistry
Bo Zhao, Mahalia A C Serrano, Jingjing Gao, Jiaming Zhuang, Richard W Vachet, S Thayumanavan
Amphiphilic random co-polymers, which form stable reverse micelle-type assemblies, have been designed and synthesized. We demonstrate that the reverse micelles, formed by these co-polymers are capable of selectively binding peptides through electrostatic interactions, indicating that these random polymers can self-organize into functionally selective materials. Moreover, these random co-polymers also enable the ordered co-crystallization of matrix and extracted guest molecules, giving rise to substantial signal enhancements during MALDI-MS detection...
March 7, 2018: Polymer Chemistry
Abeer A Alzahrani, Mohand Saed, Christopher M Yakacki, Han Byul Song, Nancy Sowan, Joshua J Walston, Parag K Shah, Matthew K McBride, Jeffrey W Stansbury, Christopher N Bowman
This study is the first to employ the use of the copper-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization to form a tough and stiff, porous material from a well-defined network possessing a high glass transition temperature. The effect of the network linkages formed as a product of the CuAAC reaction, i.e., the triazoles, on the mechanical behavior at high strain was evaluated by comparing the CuAAC foam to an epoxy-amine-based foam, which consisted of monomers with similar backbone structures and mechanical properties (i...
January 7, 2018: Polymer Chemistry
Bonnie L Buss, Logan R Beck, Garret M Miyake
Synthetic routes to higher ordered polymeric architectures are important tools for advanced materials design and realization. In this study, organocatalyzed atom transfer radical polymerization is employed for the synthesis of star polymers through a core-first approach using a visible-light absorbing photocatalyst, 3,7-di(4-biphenyl)-1-naphthalene-10-phenoxazine. Structurally similar multifunctional initiators possessing 2, 3, 4, 6, or 8 initiating sites were used in this study for the synthesis of linear telechelic polymers and star polymers typically possessing dispersities lower than 1...
2018: Polymer Chemistry
In-Hwan Lee, Emre H Discekici, Shelby L Shankel, Athina Anastasaki, Javier Read de Alaniz, Craig J Hawker, David J Lunn
We report a simple and efficient transformation of thiol and thiocarbonylthio functional groups to bromides using stable and commercially available brominating reagents. This procedure allows for the quantitative conversion of a range of small molecule thiols (including primary, secondary and tertiary) to the corresponding bromides under mild conditions, as well as the facile chain-end modification of polystyrene (PS) homopolymers and block copolymers prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization...
December 14, 2017: Polymer Chemistry
Pawel Krys, Marco Fantin, Patrícia V Mendonça, Carlos M R Abreu, Tamaz Guliashvili, Jaquelino Rosa, Lino O Santos, Arménio C Serra, Krzysztof Matyjaszewski, Jorge F J Coelho
The mechanism of atom transfer radical polymerization (ATRP) mediated by sodium dithionite (Na2 S2 O4 ), with CuII Br2 /Me6 TREN as catalyst (Me6 TREN: tris[2-(dimethylamino)ethyl]amine)) in ethanol/water mixtures, was investigated experimentally and by kinetic simulations. A kinetic model was proposed and the rate coefficients of the relevant reactions were measured. The kinetic model was validated by the agreement between experimental and simulated results. The results indicated that the polymerization followed the SARA ATRP mechanism, with a SO2 •- radical anion derived from Na2 S2 O4 , acting as both supplemental activator (SA) of alkyl halides and reducing agent (RA) for CuII /L to regenerate the main activator CuI /L...
November 14, 2017: Polymer Chemistry
L P D Ratcliffe, K J Bentley, R Wehr, N J Warren, B R Saunders, S P Armes
The recent development of polymerization-induced self-assembly (PISA) has facilitated the rational synthesis of a range of diblock copolymer worms, which hitherto could only be prepared via traditional post-polymerization processing in dilute solution. Herein we explore a new synthetic route to aqueous dispersions of cationic disulfide-functionalized worm gels. This is achieved via the PISA synthesis of poly[(glycerol monomethacrylate- stat -glycidyl methacrylate)]- block -poly(2-hydroxypropyl methacrylate) (P(GMA- stat -GlyMA)-PHPMA) block copolymer worms via reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization of HPMA...
October 14, 2017: Polymer Chemistry
Renhua Deng, Yin Ning, Elizabeth R Jones, Victoria J Cunningham, Nicholas J W Penfold, Steven P Armes
Herein we demonstrate that dynamic covalent chemistry can be used to induce reversible morphological transitions in block copolymer nano-objects and hydrogels. Poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA) diblock copolymer nano-objects (vesicles or worms) were prepared via polymerization-induced self-assembly. Addition of 4-carboxyphenylboronic acid (CPBA) leads to the formation of phenylboronate ester bonds with the 1,2-diol pendent groups on the hydrophilic PGMA stabilizer chains; such binding causes a subtle reduction in the packing parameter, which in turn induces either vesicle-to-worm or worm-to-sphere transitions...
September 21, 2017: Polymer Chemistry
Melissa L Hawkins, Samantha S Schott, Bagrat Grigoryan, Marc A Rufin, Bryan Khai D Ngo, Lyndsi Vanderwal, Shane J Stafslien, Melissa A Grunlan
Silicones with improved water-driven surface hydrophilicity and anti-biofouling behavior were achieved when bulk-modified with poly(ethylene oxide) (PEO) -silane amphiphiles of varying siloxane tether length: α-(EtO)3 Si-(CH2 )2 -oligodimethylsiloxane m - block -poly(ethylene oxide)8 -OCH3 ( m = 0, 4, 13, 17, 24, and 30). A PEO8 -silane [α-(EtO)3 Si-(CH2 )3 -PEO8 -OCH3 ] served as a conventional PEO-silane control. To examine anti-biofouling behavior in the absence versus presence of water-driven surface restructuring, the amphiphiles and control were surface-grafted onto silicon wafers and used to bulk-modify a medical-grade silicone, respectively...
September 14, 2017: Polymer Chemistry
J L Ungerleider, J K Kammeyer, R L Braden, K L Christman, N C Gianneschi
The targeted delivery of enzyme-responsive nanoparticles to specific tissues can be a valuable, minimally invasive approach for imaging or drug delivery applications. In this study, we show for the first time enzyme-directed assembly of intravenously (IV) delivered nanoparticles in ischemic skeletal muscle, which has applications for drug delivery to damaged muscle of the type prevalent in peripheral artery disease (PAD). Specifically, micellar nanoparticles are cleavable by matrix metalloproteinases (MMPs), causing them to undergo a morphological switch and thus aggregate in tissues where these enzymes are upregulated, like ischemic muscle...
September 14, 2017: Polymer Chemistry
Jawaher A Alfurhood, Hao Sun, Christopher P Kabb, Bryan S Tucker, James H Matthews, Hendrik Luesch, Brent S Sumerlin
We report nanoassemblies based on block copolymers of N -(2-hydroxypropyl) methacrylamide (HPMA) in which drug cleavage enhances the biological compatibility of the original polymer carrier by regeneration of HPMA units. Drug release via ester hydrolysis suggests this approach offers potential for stimuli-responsive drug delivery under acidic conditions.
September 14, 2017: Polymer Chemistry
Daniel N Crisan, Oliver Creese, Ranadeb Ball, Jose Luis Brioso, Ben Martyn, Javier Montenegro, Francisco Fernandez-Trillo
Here we present the synthesis and post-polymerisation modification of poly(acryloyl hydrazide), a versatile scaffold for the preparation of functional polymers: poly(acryloyl hydrazide) was prepared from commercially available starting materials in a three step synthesis on a large scale, in good yields and high purity. Our synthetic approach included the synthesis of a Boc-protected acryloyl hydrazide, the preparation of polymers via RAFT polymerisation and the deprotection of the corresponding Boc-protected poly(acryloyl hydrazide)...
August 20, 2017: Polymer Chemistry
Samantha J Paluck, Heather D Maynard
Fibroblast growth factor-2 (FGF2) is a heparin binding protein that plays a role in a range of biological functions such as wound healing and bone regeneration. Heparin, a highly sulfated glycosaminoglycan, is required for FGF2 to bind to its receptor. Therefore, polymeric mimics of heparin are widely studied for their ability to manipulate FGF2-induced biological interactions. It is known that altering the degree of sulfonated monomer incorporation and size of heparin-mimicking polymers can affect protein-receptor binding...
August 20, 2017: Polymer Chemistry
Parag K Shah, Jeffrey W Stansbury, Christopher N Bowman
A new addition-fragmentation chain transfer (AFT) capable moiety was incorporated into a dimethacrylate monomer that participated readily in network formation by copolymerizing with multifunctional methacrylates or acrylates. The process of AFT occurred simultaneously with photopolymerization of the AFT monomer (AFM) and other (meth)acrylate monomers leading to polymer stress relaxation via network reconfiguration. At low loading levels of the AFM, a significant reduction in shrinkage stress, especially for acrylate monomers, was observed with nominal effects on conversion...
August 14, 2017: Polymer Chemistry
Abhishek U Shete, Christopher J Kloxin
An interpenetrating polymeric network (IPN) is formed in a one-pot blue-light activated scheme, where the step- and chain- growth polymerizations of the CuAAC and methacrylate reactions, respectively, are simultaneously triggered but proceed sequentially. The glassy IPN is polymerized under ambient conditions and is able to withstand high strain before failure owing to its significantly enhanced toughness. Additionally, this material exhibits shape memory attributes with readily tunable mechanical properties at high temperature...
June 28, 2017: Polymer Chemistry
Lewis D Blackman, Kay E B Doncom, Matthew I Gibson, Rachel K O'Reilly
Polymerization-induced self-assembly (PISA) is an emerging industrially relevant technology, which allows the preparation of defined and predictable polymer self-assemblies with a wide range of morphologies. In recent years, interest has turned to photoinitiated PISA processes, which show markedly accelerated reaction kinetics and milder conditions, thereby making it an attractive alternative to thermally initiated PISA. Herein, we attempt to elucidate the differences between these two initiation methods using isothermally derived phase diagrams of a well-documented poly(ethylene glycol)- b -(2-hydroxypropyl methacrylate) (PEG- b -HPMA) PISA system...
May 14, 2017: Polymer Chemistry
Dakota J Suchyta, Robert J Soto, Mark H Schoenfisch
Chitosan was selectively monophosphorylated via reaction with phosphorus oxychloride (POCl3 ) to enhance water solubility while avoiding polyphosphate formation. The use of POCl3 resulted in negligible product degradation (i.e., breakdown of O -glycosidic bonds) even after a 3 d reaction period (<5% weight loss). X-ray photoelectron spectroscopy (XPS) characterization of the POCl3 -phosphorylated chitosan (P-chitosan) revealed a phosphorus to nitrogen (P/N) atomic ratio of 0.30. Phosphorus-31 nuclear magnetic resonance (31 P NMR) spectroscopy verified the monophosphorylation of chitosan's primary and secondary alcohols, and primary amines...
April 28, 2017: Polymer Chemistry
Jozsef Kupai, Mayamin Razali, Sibel Buyuktiryaki, Rustem Kecili, Gyorgy Szekely
Molecularly imprinted materials are man-made mimics of biological receptors. Their polymer network has recognition sites complementary to a substrate in terms of size, shape and chemical functionality. They have diverse applications in various chemical, biomedical and engineering fields such as solid phase extraction, catalysis, drug delivery, pharmaceutical purification, (bio)sensors, water treatment, membrane separations and proteomics. The stability and reusability of molecularly imprinted polymers (IPs) have crucial roles in developing applications that are reliable, economic and sustainable...
January 28, 2017: Polymer Chemistry
Carlos M R Abreu, Liye Fu, Sheiliza Carmali, Arménio C Serra, Krzysztof Matyjaszewski, Jorge F J Coelho
Aqueous supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) using inorganic sulfites was successfully carried out for the first time. Under optimized conditions, a well-controlled poly[oligo(ethylene oxide) methyl ether acrylate] (POEOA) was obtained with <30 ppm of soluble copper catalyst using tris(2-pyridylmethyl)amine (TPMA) ligand in the presence of an excess of halide salts (e.g. NaCl). Inorganic sulfites (e.g. Na2 S2 O4 ) were continuously fed into the reaction mixture...
January 14, 2017: Polymer Chemistry
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