Co-reporter:Wei Lu;Yangyang Wang;Weiyu Wang;Shiwang Cheng;Jiahua Zhu;Yuewen Xu;Kunlun Hong;Nam-Goo Kang;Jimmy Mays
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 37) pp:5741-5748
Publication Date(Web):2017/09/26
DOI:10.1039/C7PY01225J
All acrylic-based thermoplastic elastomers (TPEs) offer potential alternatives to the widely-used styrenic TPEs. However, the high entanglement molecular weight (Me) of polyacrylates, as compared to polydienes, leads to “disappointing” mechanical performance as compared to styrenic TPEs. In this study, triblock copolymers composed of alkyl acrylates with different pendant groups and different glass transition temperatures (Tgs), i.e. 1-adamatyl acrylate (AdA) and tetrahydrofurfuryl acrylate (THFA), were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization. Thermal characterization of the resulting polymers was performed using differential scanning calorimetry (DSC), and the Tgs of both segments were observed for the block copolymers. This indication of microphase separation behavior was further demonstrated using atomic-force microscopy (AFM) and small angle X-ray scattering (SAXS). Dynamic mechanical analysis (DMA) showed that the softening temperature of the PAdA domains is 123 °C, which is higher than that of both styrenic TPEs and commercial acrylic based TPEs with poly(methyl methacrylate) (PMMA) hard block. The resulting triblock copolymers also exhibited stress–strain behavior superior to that of conventional all acrylic-based TPEs composed of PMMA and poly(n-butyl acrylate) (PBA) made by controlled radical processes, while the tensile strength was lower than for products made by living anionic polymerization.
Co-reporter:Andrew Goodwin, Weiyu Wang, Nam-Goo Kang, Yangyang Wang, Kunlun Hong, and Jimmy Mays
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 39) pp:9566-9576
Publication Date(Web):August 21, 2015
DOI:10.1021/acs.iecr.5b02560
We present the synthesis of poly(n-butyl acrylate)-g-poly(methyl methacrylate) (PnBA-g-PMMA) multigraft copolymers via a grafting-through (macromonomer) approach. The synthesis was performed using two controlled polymerization techniques. The PMMA macromonomer was obtained by high-vacuum anionic polymerization followed by the copolymerization of n-butyl acrylate and PMMA macromonomer using reversible addition–fragmentation chain transfer (RAFT) polymerization to yield the desired all-acrylic multigraft structures. The PnBA-g-PMMA multigraft structures exhibit randomly spaced branch points with various PMMA contents, ranging from 15 to 40 vol %, allowing an investigation into how physical properties vary with differences in the number of branch points and molecular weight of grafted side chains. The determination of molecular weight and polydispersity indices of both the PMMA macromonomer and the graft copolymers was carried out using size exclusion chromatography with triple detection, and the structural characteristics of both the macromonomer and PnBA-g-PMMA graft materials were characterized by 1H and 13C NMR. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was employed for monitoring the macromonomer synthesis. Thermal characteristics of the materials were analyzed using differential scanning calorimetry and thermogravimetric analysis. The mechanical performance of the graft materials was characterized by rheology and dynamic mechanical analysis, revealing that samples with PMMA content of 25–40 vol % exhibit superior elastomeric properties as compared to materials containing short PMMA side chains or <25 vol % PMMA. Lastly, atomic force microscopy showed a varying degree of microphase separation between the glassy and rubbery components that is strongly dependent on PMMA side chain molecular weight.
Co-reporter:Wenwen Wang, Weiyu Wang, Hui Li, Xinyi Lu, Jihua Chen, Nam-Goo Kang, Qiuyu Zhang, and Jimmy Mays
Industrial & Engineering Chemistry Research 2015 Volume 54(Issue 4) pp:1292-1300
Publication Date(Web):January 14, 2015
DOI:10.1021/ie504457e
In this work, high molecular weight “comb-shaped” graft copolymers, poly(isoprene-g-styrene), with polyisoprene as the backbone and polystyrene as side chains, were synthesized via free radical emulsion polymerization by copolymerization of isoprene with a polystyrene macromonomer synthesized using anionic polymerization. A small amount of toluene was used in order to successfully disperse the macromonomer. Both a redox and thermal initiation system were used in the emulsion polymerization, and the latex particle size and distribution were investigated by dynamic light scattering. The structural characteristics of the macromonomer and comb graft copolymers were investigated through use of size exclusion chromatography, spectroscopy, microscopy, thermal analysis, and rheology. While the macromonomer was successfully copolymerized to obtain the desired multigraft copolymers, small amounts of unreacted macromonomer remained in the products, reflecting its reduced reactivity due to steric effects. Nevertheless, the multigraft copolymers obtained were very high in molecular weight (5–12 × 105 g/mol) and up to 10 branches per chain, on average, could be incorporated. A material incorporating 29 wt % polystyrene exhibits a disordered microphase separated morphology and elastomeric properties. These materials show promise as new, highly tunable, and potentially low cost thermoplastic elastomers.
Co-reporter:Andrew Goodwin, Sachin Bobade, Nam-Goo Kang, Durairaj Baskaran, Kunlun Hong and Jimmy Mays
RSC Advances 2015 vol. 5(Issue 8) pp:5611-5616
Publication Date(Web):18 Dec 2014
DOI:10.1039/C4RA11568F
This work presents a three-step synthetic procedure to obtain a hypergrafted copolymer composed of a glassy backbone with flexible branched pendant segments. The desired hypergrafted structure was obtained by using a polyfunctional macroinitiator, linear poly(styrene-co-4-hydroxystyrene), to yield polystyrene-graft-hyperbranched polyglycidol with randomly placed branch junctions. Atomic force microscopy, dynamic light scattering, and viscometry probed the aggregation and viscometric behavior of the polymer in DMF and DMF–LiBr solutions. The polymer exhibited polyelectrolyte behavior demonstrated by a large increase in the reduced viscosity prior to neutralization with LiBr salt. Additionally, conformational changes were observed by dynamic light scattering in both the average aggregate size and aggregate population with the addition of LiBr salt.
Co-reporter:Adam Imel, Thomas Malmgren, Mark Dadmun, Samuel Gido, Jimmy Mays
Biomaterials 2015 73() pp: 131-141
Publication Date(Web):
DOI:10.1016/j.biomaterials.2015.09.015
Co-reporter:Suxiang Deng, Mohammad K. Hassan, Kenneth A. Mauritz, Jimmy W. Mays
Polymer 2015 Volume 73() pp:17-24
Publication Date(Web):2 September 2015
DOI:10.1016/j.polymer.2015.07.030
High temperature fuel cell membranes based on poly(1,3-cyclohexadiene) were prepared by a Polymerization-Crosslinking-Sulfonation (PCS) approach, and a broad range of membrane compositions were achieved using various sulfonating reagents and reaction conditions. Membranes were characterized for their proton conductivity and thermal degradation behavior. Some of the membranes showed up to a 68% increase in proton conductivity as compared to Nafion under the same conditions (100% relative humidity and 120 °C). Thermogravimetric analysis revealed that these membranes are thermally stable up to 200 °C. High proton conductivity and thermal stability, combined with much lower cost as compared to Nafion®, make these materials potentially interesting as fuel cell membranes, although they are chemically vulnerable under fuel cell operation conditions.
Co-reporter:Vikram K. Srivastava;Ronald A. Quinlan;Alexer L. Agapov;John R. Dunlap;Kimberly M. Nelson;Edward Duranty;Alexei P. Sokolov;Gajanan S. Bhat
Advanced Functional Materials 2014 Volume 24( Issue 31) pp:4969-4977
Publication Date(Web):
DOI:10.1002/adfm.201400484
The excellent properties exhibited by monolayer graphene have spurred the development of exfoliation techniques using bulk graphite to produce large quantities of pristine monolayer sheets. Development of simple chemistry to exfoliate and intercalate graphite and graphite mimics in large quantities is required for numerous applications. To determine the macroscopic behavior of restacked, exfoliated bulk materials, a systematic approach is presented using a simple, redox-liquid sonication process along to obtain large quantities of 2D and 3D hexagonally layered graphite, molybdenum disulfide, and boron nitride, which are subsequently characterized to observe chemical and structural changes. For MoS2 sonicated with the antioxidant sodium bisulfite, results from Raman spectroscopy, X-ray diffraction, and electron microscopy indicate the presence of distorted phases from different polymorphs, and apparent nanotube structures in the bulk, restacked powder. Furthermore, using thermograviemtric analysis, the antioxidant enhances the resistance to oxidative degradation of MoS2, upon thermal treatment up to 900 °C. The addition of the ionic antioxidant decreased dispersion stability in non-polar solvent, suggesting decreased compatibility with non-polar systems. Using simple chemical methods, the ability to generate tailored multidimensional layered materials with unique macroscopic properties is critical for numerous applications, including electrical devices, reinforced polymer composites, lithium–ion capacitors, and chemical sensing.
Co-reporter:Xiaojun Wang, Jihua Chen, Kunlun Hong, and Jimmy W. Mays
ACS Macro Letters 2012 Volume 1(Issue 6) pp:743
Publication Date(Web):June 1, 2012
DOI:10.1021/mz300192u
The synthesis and characterization of well-defined polyacid based block copolymers containing polyisoprene (PI) are reported. The challenge of maintaining the integrity of the polydiene while producing polyacid from the tert-butyl ester precursor is addressed in this communication. A general purification method was also developed, taking advantage of the different polarities of each block. The polystyrene-b-polyisoprene-b-poly(acrylic acid) (PS-b-PI-b-PAA) triblock terpolymers form multicompartmental micelles via aqueous self-assembly. Our work reveals the morphological consequences of unique balances among global and local interactions.
Co-reporter:Xiaojun Wang, Monojoy Goswami, Rajeev Kumar, Bobby G. Sumpter and Jimmy Mays
Soft Matter 2012 vol. 8(Issue 11) pp:3036-3052
Publication Date(Web):08 Feb 2012
DOI:10.1039/C2SM07223H
This article reviews current experimental observations and theoretical calculations devoted towards understanding micro-phase separation in charged block copolymer systems. We discuss bulk morphologies in melt and in solution, as well as some of the new emerging research directions. Overall, a comprehensive picture is beginning to emerge on the fundamental role of electrostatics in the micro-phase separation of charged block copolymers. This understanding provides exciting new insight that may be used to direct targeted structures that endow the materials with desired properties that can have tremendous potential in technological applications.
Co-reporter:Tianzi Huang, Xiaojun Wang, Thomas Malmgren, Jimmy W. Mays
European Polymer Journal 2012 Volume 48(Issue 3) pp:632-636
Publication Date(Web):March 2012
DOI:10.1016/j.eurpolymj.2012.01.003
In order to improve their thermal stability, poly(1,3-cyclohexadiene) (PCHD) homopolymer, diblock copolymer of PCHD with styrene (PCHD-b-PS), and crosslinked PCHD membranes were dehydrogenated by addition of bromine to the polymer in solution, followed by dehydrobromination using an isothermal treatment at elevated temperature. The brominated PCHD materials thus obtained were characterized via FT-IR and thermogravimetric analysis (TGA) before and after dehydrobromination. Dehydrobromination was performed inside a TGA instrument, allowing insight into thermal stability of the analytes to be obtained. The dehydrobrominated PCHD samples were characterized using elemental analysis, and it was found the dehydrogenation of PCHD to polyphenylene was not complete. Nevertheless, some aromatization did occur, and the thermal stability of the treated polymer was greatly enhanced as compared to its PCHD precursor. Such materials may thus be of interest as high carbon content, graphene-like films. Crosslinked PCHD membranes and PCHD-b-PS diblock copolymers were treated via the same bromination/pyrolysis process, which resulted in markedly improved thermal stabilities for these materials as well.Graphical abstractHighlights► We treated poly(cyclohexadiene) materials by bromination/debromination. ► Thermal stability of the treated polymer was greatly enhanced. ► Dehydrogenation to polyphenylene was not complete. ► Some aromatization did occur. ► Such materials are of interest as high carbon, graphene-like films.
Co-reporter:Tianzi Huang;Xiaojun Wang;Thomas Malmgren;Kunlun Hong
Macromolecular Chemistry and Physics 2012 Volume 213( Issue 1) pp:49-56
Publication Date(Web):
DOI:10.1002/macp.201100548
Abstract
Linear PCHD and polyisoprenes with different microstructures and molecular weights are synthesized and chemically modified to improve their thermal and chemical stability by forming a three-membered ring structure containing two C–F bonds. Pyrolysis of these fluorinated polydienes proceeds through a two-stage decomposition involving chain scission, crosslinking, dehydrogenation, and dehalogenation. The pyrolysis leads to graphite-like residues, whereas their polydiene precursors decompose completely under the same conditions. The fluorination of PCHD enhances its thermal stability. The stronger C–F bond along with high strain of the three-membered ring structure and formation of relatively stable free radicals play an important role in the thermal stability of fluorinated polydienes.
Co-reporter:Tianzi Huang;Xiaojun Wang;Thomas Malmgren;Kunlun Hong
Macromolecular Chemistry and Physics 2012 Volume 213( Issue 1) pp:
Publication Date(Web):
DOI:10.1002/macp.201290003
Co-reporter:Tianzi Huang;Jamie M. Messman;Kunlun Hong
Journal of Polymer Science Part A: Polymer Chemistry 2012 Volume 50( Issue 2) pp:338-345
Publication Date(Web):
DOI:10.1002/pola.25037
Abstract
Diblock copolymers of polystyrene-block-(1,3-cyclohexadiene) (PS-b-PCHD), with varied molecular weights and compositions, were synthesized by sequential polymerization of styrene and 1,3-cyclohexadiene (CHD) initiated by sec-butyllithium in cyclohexane in the presence of appropriate additives during formation of the PCHD block. The residual double bonds in the PCHD block were saturated by addition of in situ generated difluorocarbene and/or hydrogen to enhance thermal and chemical stability. The fluorinated and/or hydrogenated polydiene blocks were chemically stable, allowing for controlled sulfonation of the PS blocks using acetyl sulfate. 1H NMR and FT-IR characterization confirmed successful fluorination/hydrogenation and sulfonation of the respective blocks. The resulting amphiphilic block copolymers consist of a semiflexible fluorine-containing hydrophobic block having a bridged double ring structure and a hydrophilic sulfonated PS block. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Co-reporter:Jimmy W. Mays, Rajeev Kumar, Scott W. Sides, Monojoy Goswami, Bobby G. Sumpter, Kunlun Hong, Xiaodong Wu, Thomas P. Russell, Samuel P. Gido, Apostolos Avgeropoulos, Thodoris Tsoukatos, Nikos Hadjichristidis, Frederick L. Beyer
Polymer 2012 Volume 53(Issue 22) pp:5155-5162
Publication Date(Web):12 October 2012
DOI:10.1016/j.polymer.2012.08.047
Concerted experimental and theoretical investigations have been carried out to understand the microphase separation in diblock copolymer melts containing poly (1,3-cyclohexadiene), PCHD, as one of the constituents. In particular, we have studied diblock copolymer melts containing polystyrene (PS), polybutadiene (PB), and polyisoprene (PI) as the second block. We have systematically varied the ratio of 1,2-/1,4-microstructures of poly (1,3-cyclohexadiene) to tune the conformational asymmetry between the two blocks and characterized the effects of these changes on the morphologies using transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). Our experimental investigations reveal that the melts of PCHD-b-PB, PCHD-b-PS and PCHD-b-PI containing nearly equal fractions of each component and high percentage of 1,4-microstructures in the PCHD block form cylindrical rather than lamellar morphologies as expected in symmetric diblock copolymers. In contrast, the morphologies of PCHD-b-PB, PCHD-b-PS and PCHD-b-PI containing PCHD block with higher 1,2-microstructure are found to be disordered at 110 °C. The change in the morphological behavior is in good agreement with our numerical calculations using the random phase approximation and self-consistent field theory for conformationally asymmetric diblock copolymer melts. Also, the effects of composition fluctuations are studied by extending the Brazovskii–Leibler–Fredrickson–Helfand (J. Chem. Phys. 87, 697 (1987)) theory to conformationally asymmetric diblock copolymer melts. These results allow the understanding of the underlying self-assembly process that highlights the importance of the conformational asymmetry in tuning the morphologies in block copolymers.Graphical abstract
Co-reporter:Xiaojun Wang, Kunlun Hong, Durairaj Baskaran, Monojoy Goswami, Bobby Sumpter and Jimmy Mays
Soft Matter 2011 vol. 7(Issue 18) pp:7960-7964
Publication Date(Web):26 Jul 2011
DOI:10.1039/C1SM06040F
Block copolymers of fluorinated isoprene and partially sulfonated styrene form novel tapered rods and ribbon-like micelles in aqueous media due to a distribution of sulfonation sites and a large Flory–Huggins interaction parameter. A combination of microscopy, light scattering, and simulation demonstrates the presence of these unique nanostructures. This study sheds light on the micellization behavior of amphiphilic block polymers by revealing a new mechanism of self-assembly.
Co-reporter:Madhuvanthi A. Kandadai, Rajasekhar Anumolu, Xiaojun Wang, Durairaj Baskaran, Leonard F. Pease III, Dmitry Bedrov, Grant D. Smith, Jimmy W. Mays, Jules J. Magda
European Polymer Journal 2011 Volume 47(Issue 10) pp:2022-2027
Publication Date(Web):October 2011
DOI:10.1016/j.eurpolymj.2011.07.017
Rheological evidence is provided demonstrating that covalent grafting of monodisperse isotactic poly(l-leucine) branches onto linear hyaluronan (HA) polysaccharide chains yields comb-branched HA chains that self-assemble into long-lived physical networks in aqueous solutions driven by hydrophobic interactions between poly(l-leucine) chains. This is in stark contrast to native (unmodified) HA solutions which exhibit no tendency to form long-lived physical networks.Graphical abstractHighlights► Poly (l-Leucine) grafted HA chains self assemble into physical networks. ► This network has an elastic shear modulus ≈ 100 Pa and a loss tangent ≈ 0.25. ► It has a network lifetime > 20 s. ► It exhibits almost complete elastic strain recovery after removal of shear stress. ► No physical network formation seen in unmodified HA.
Co-reporter:Akinbode I. Isaacs Sodeye, Tianzi Huang, Samuel P. Gido, Jimmy W. Mays
Polymer 2011 Volume 52(Issue 14) pp:3201-3208
Publication Date(Web):22 June 2011
DOI:10.1016/j.polymer.2011.05.012
Small-angle neutron scattering (SANS) and ultra-small-angle X-ray scattering (USAXS) have been used to study the structural changes in fluorinated polyisoprene/sulfonated polystyrene (FISS) diblock copolymers as they evolved from the dry state to the water swollen state. A dilation of the nanometer-scale hydrophilic domains has been observed as hydration increased, with greater dilation occurring in the more highly sulfonated samples or upon hydration at higher temperatures. Furthermore, a decrease in the order in these phase separated structures is observed upon swelling. The glass transition temperatures of the fluorinated blocks have been observed to decrease upon hydration of these materials, and at the highest hydration levels, differential scanning calorimetry (DSC) has shown the presence of tightly bound water. A precipitous drop in the mechanical integrity of the 50% sulfonated materials is also observed upon exceeding the glass transition temperature (Tg), as measured by dynamic mechanical analysis (DMA).
Co-reporter:Akinbode I. Isaacs Sodeye, Tianzi Huang, Samuel P. Gido, Jimmy W. Mays
Polymer 2011 Volume 52(Issue 24) pp:5393-5396
Publication Date(Web):10 November 2011
DOI:10.1016/j.polymer.2011.10.005
In this study, block copolymer ionomers of the cesium salt (20 mol %) of fluorinated polyisoprene-block-sulfonated polystyrene were spin cast into membranes and annealed under an electric field of ∼40 V/μm at 130 °C for 24 h. The effect of this treatment was a 2.5 times increase in the ionic conductivity as measured by electrochemical impedance spectroscopy, under all humidity conditions measured. This can be attributed to the increased connectivity of the ionic domains of the block copolymers. This E-field alignment technique may thus find application in the fabrication of nanostructured polyelectrolytes with enhanced charge transport capacity.
Co-reporter:Xiaojun Wang, Jamie Messman, Jimmy W. Mays, and Durairaj Baskaran
Biomacromolecules 2010 Volume 11(Issue 9) pp:
Publication Date(Web):August 6, 2010
DOI:10.1021/bm1004146
Poly(l-leucine) grafted hyaluronan (HA-g-PLeu) has been synthesized via a Michael addition reaction between primary amine terminated poly(l-leucine) and acrylate-functionalized HA (TBAHA−acrylate). The precursor hyaluronan was first functionalized with acrylate groups by reaction with acryloyl chloride in the presence of triethylamine in N,N-dimethylformamide. 1H NMR analysis of the resulting product indicated that an increase in the concentration of acryloylchoride with respect to hydroxyl groups on HA has only a moderate effect on functionalization efficiency, f. A precise control of stoichiometry was not achieved, which could be attributed to partial solubility of intermolecular aggregates and the hygroscopic nature of HA. Michael addition at high [PLeu-NH2]/[acrylate]TBAHA ratios gave a molar grafting ratio of only 0.20 with respect to the repeat unit of HA, indicating grafting limitation due to insolubility of the grafted HA-g-PLeu. Soluble HA-g-PLeu graft copolymers were obtained for low grafting ratios (<0.039) with <8.6% by mass of PLeu and were characterized thoroughly using light scattering, 1H NMR, FT-IR, and AFM techniques. Light scattering experiments showed a strong hydrophobic interaction between PLeu chains, resulting in aggregates with segregated nongrafted HA segments. This yields local networks of aggregates, as demonstrated by atomic force microscopy. Circular dichroism spectroscopy showed a β-sheet conformation for aggregates of poly(l-leucine).
Co-reporter:Georgios Sakellariou, Apostolos Avgeropoulos, Nikos Hadjichristidis, Jimmy W. Mays, Durairaj Baskaran
Polymer 2009 50(26) pp: 6202-6211
Publication Date(Web):
DOI:10.1016/j.polymer.2009.10.038
Co-reporter:Georgios Sakellariou, Haining Ji, Jimmy W. Mays, Nikos Hadjichristidis and Durairaj Baskaran
Chemistry of Materials 2007 Volume 19(Issue 26) pp:6370
Publication Date(Web):November 21, 2007
DOI:10.1021/cm702470x
Co-reporter:Haining Ji;Georgios Sakellariou;Rigoberto C. Advincula;Grant D. Smith;S. Michael Kilbey II;Mark D. Dadmun
Journal of Polymer Science Part A: Polymer Chemistry 2007 Volume 45(Issue 17) pp:3949-3955
Publication Date(Web):17 JUL 2007
DOI:10.1002/pola.22148
This article describes the synthesis and characterization of [polystyrene-b-poly(2-vinylpyridine)]n star-block copolymers with the poly(2-vinylpyridine) blocks at the periphery. A two-step living anionic polymerization method was used. Firstly, oligo(styryl)lithium grafted poly(divinylbenzene) cores were used as multifunctional initiators to initiate living anionic polymerization of styrene in benzene at room temperature. Secondly, vinylpyridine was polymerized at the periphery of these living (polystyrene)n stars in tetrahydrofuran at −78 °C. The resulting copolymers were characterized using size exclusion chromatography, multiangle laser light scattering, 1H NMR, elemental analysis, and intrinsic viscosity measurements. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3949–3955, 2007
Co-reporter:Il-Doo Chung, Philip Britt, Dong Xie, Eva Harth and Jimmy Mays
Chemical Communications 2005 (Issue 8) pp:1046-1048
Publication Date(Web):10 Jan 2005
DOI:10.1039/B416591H
Well-defined acryloyl β-alanine (ABA) polymers were synthesized directly via atom transfer radical polymerization (ATRP) under near physiological conditions using various water soluble initiators with high yield and narrow molecular weight distributions.
Co-reporter:Ken Terao, Jimmy W Mays
European Polymer Journal 2004 Volume 40(Issue 8) pp:1623-1627
Publication Date(Web):August 2004
DOI:10.1016/j.eurpolymj.2004.03.010
On-line two-angle (15° and 90°) light scattering measurements with a gel permeation chromatography for linear and branched polystyrene in tetrahydrofuran (a good solvent) and in trans-decalin (a theta solvent) were made and compared with data from a multi-angle light scattering detector and literature values. Theoretically, weight-average molecular weight and the radius of gyration Rg can be determined accurately in the range where Rg2k2 is less than 1.2 (rod)∼1.7 (random coil); here, k is the absolute value of the scattering vector for a right angle detector with the Berry square root method. Molecular weight dependence of the radius of gyration obtained from the two-angle light scattering detector for linear and branched polystyrenes under different thermodynamic conditions were measured and found to be almost the same as values measured with a multi-angle light scattering detector and literature values in the appropriate range of molecular weight.
Co-reporter:Hongwei Zhang, Kunlun Hong, Michael Jablonsky and Jimmy W. Mays
Chemical Communications 2003 (Issue 12) pp:1356-1357
Publication Date(Web):09 May 2003
DOI:10.1039/B301562A
Use of a room temperature ionic liquid as the medium for conventional free radical copolymerization of styrene and methyl methacrylate resulted in reactivity ratios that were significantly different from those obtained in conventional organic solvents or in bulk, demonstrating that polymerization in this alternative medium offers potential to create copolymers having new monomer sequences.
Co-reporter:Kunlun Hong, Hongwei Zhang, Jimmy W. Mays, Ann E. Visser, Christopher S. Brazel, John D. Holbrey, W. Matthew Reichert and Robin D. Rogers
Chemical Communications 2002 (Issue 13) pp:1368-1369
Publication Date(Web):23 May 2002
DOI:10.1039/B204319J
Free-radical polymerization of methyl methacrylate and styrene using conventional organic initiators in the room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) is rapid and produces polymers with molecular weights up to 10× higher than from benzene; both polymerization and isolation of products were achieved without using VOCs, offering economic as well as environmental advantages.
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