bluuebunny/crossref_metadata_2025_split huggingface dataset:
Syntheses and alignment behavior of liquid crystalline polymethacrylates having 2‐ and 4‐styrylpyridine moieties
Authors: Kwak Giseop , Kim Min‐Woo , Park Deok‐Ha , Kong Jong‐Yun , Hyun Seok‐Hee , Kim Woo‐Sik 
Published: July 2008

AbstractTwo kinds of polymethacrylates, 1 and 2, with 2‐styrylpyridine and 4‐styrylpyridine moiety as a photoreactive group, which have a benzoate group as a mesogenic unit, and hexylene group as a flexible spacer in the same side chain, were synthesized to characterize their alignment behaviors. The UV absorption and fluorescence studies on the two polymers revealed that the latter polymer with the 4‐stylrylpyridine moiety is more aggregative than the former polymer with the 2‐styrylpyridine moiety. The polymer 1 showed a nematic phase structure at 170 °C, while 2 appeared in a partially bilayered smectic A phase structure in the homeotropic direction at 175 °C. The polymer 1 film generated an in‐plane alignment by a linearly polarized UV light irradiation and subsequent annealing, and its direction was parallel with respect to the irradiation. On the other hand, the polymer 2 film with the same treatments gave a high out‐of‐plane order parameter of 0.73 in a wide temperature range of 120–240 °C. The significant differences in the aggregation behavior, the liquid‐crystalline structure, and the alignment between the two polymers were discussed by the structural differences between the 2‐ and 4‐styrylpyridine moieties in the two polymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5371–5380, 2008
In situ polymerization of ethylene using metallocene catalysts: Effect of clay pretreatment on the properties of highly filled polyethylene nanocomposites
Authors: Leone Giuseppe , Bertini Fabio , Canetti Maurizio , Boggioni Laura , Stagnaro Paola , Tritto Incoronata 
Published: July 2008

AbstractHighly filled polyethylene (PE)‐based nanocomposites were obtained by insitu polymerization technique. An organically modified montmorillonite, Cloisite® 15A (C15A), was previously treated with methylaluminoxane (MAO) to form a supported cocatalyst (C15A/MAO) before being contacted with a zirconocene catalyst. The main features of C15A/MAO intermediates were studied by elemental analysis, TGA, TGA‐FTIR, WAXD, and TEM. MAO reacts with the clay, replaces most of the organic surfactant within the clay galleries and destroys the typical crystrallographic order of the nanoclay. The catalytic activity in the presence of C15A/MAO is higher than in ethylene polymerization without any inorganic filler and increases with MAO supportation time. This indicates that part of the polymer chains grows within the clay galleries, separates them, and makes it possible to tune the final morphology of the composites. The polymerization results and the influence of C15A pretreatment and polymerization conditions on thermal and morphological properties of the hybrid PE/C15A nanocomposites are presented. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5390–5403, 2008
Synthesis and characterization of a novel mid‐chain macrophotoinitiator of polyacrylonitrile by Ce(IV)/HNO3 redox system
Authors: Degirmenci Mustafa , Taskesen Edip , Hicri Sirin , Yilmaz Hasim 
Published: July 2008

AbstractThe polymerization of acrylonitrile initiated by cerium(IV) ammonium nitrate in combination with dihydroxy functional photoinitiator namely, 2‐hydroxy‐1‐[4‐(2‐hydroxyethoxy)phenyl]‐2‐methyl propan‐1‐one (HE‐HMPP), Irgacure 2959, has been investigated in aqueous nitric acid. A novel mid‐chain macrophotoinitiator of polyacrylonitrile (PAN) was obtained. The effects of acrylamide (AAm), HE‐HMPP, Ce(IV), and HNO3 concentrations and temperature on the polymerization rate, monomer conversion, and intrinsic viscosities were investigated. The photodegradation and IR, H NMR, UV, and fluorescence spectroscopic studies revealed that PAN with desired photoinitiator functionality in the middle of the chain was obtained. The obtained PAN was used as prepolymer for photoinduced free radical polymerization of methyl methacrylate (MMA) and AAm to produce block copolymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5404–5413, 2008
Synthesis and characterization of well‐defined block and statistical copolymers based on lauryl methacrylate and 2‐(acetoacetoxy)ethyl methacrylate using RAFT‐controlled radical polymerization
Authors: Demetriou Maria , Krasia‐Christoforou Theodora 
Published: July 2008

AbstractFour well‐defined diblock copolymers and one statistical copolymer based on lauryl methacrylate (LauMA) and 2‐(acetoacetoxy)ethyl methacrylate (AEMA) were prepared using reversible addition‐fragmentation chain transfer (RAFT) polymerization. The polymers were characterized in terms of molecular weights, polydispersity indices (ranging between 1.12 and 1.23) and compositions by size exclusion chromatography and 1H NMR spectroscopy, respectively. The preparation of the block copolymers was accomplished following a two‐step methodology: First, well‐defined LauMA homopolymers were prepared by RAFT using cumyl dithiobenzoate as the chain transfer agent (CTA). Kinetic studies revealed that the polymerization of LauMA followed first‐order kinetics demonstrating the “livingness” of the RAFT process. The pLauMAs were subsequently used as macro‐CTA for the polymerization of AEMA. The glass transition (Tg) and decomposition temperatures (ranging between 200 and 300 °C) of the copolymers were determined using differential scanning calorimetry and thermal gravimetric analysis, respectively. The Tgs of the LauMA homopolymers were found to be around −53 °C. Block copolymers exhibited two Tgs suggesting microphase separation in the bulk whereas the statistical copolymer presented a single Tg as expected. Furthermore, the micellization behavior of pLauMA‐b‐pAEMA block copolymers was investigated in n‐hexane, a selective solvent for the LauMA block, using dynamic light scattering. pLauMA‐b‐pAEMA block copolymers formed spherical micelles in dilute hexane solutions with hydrodynamic diameters ranging between 30 and 50 nm. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5442–5451, 2008
Detitanation of MgCl2‐supported Ziegler‐Natta catalysts for the study of active sites organization
Authors: Ribour David , Monteil Vincent , Spitz Roger 
Published: July 2008

AbstractThermal treatments under vacuum of conventional supported Ziegler‐Natta precatalysts (MgCl2/TiCl4/Dibutylphthalate) were conducted to gradually remove titanium to modify the active sites distribution. Only limited detitanations of precatalysts were achieved paying attention not to chemically alter the internal donor (T < 150 °C). Used in combination with the required cocatalyst and external donor in the propylene slurry polymerization, the modified precatalysts exhibited a drop of activity versus decreasing titanium content but the distributed polymer properties are almost not affected (a slight narrowing of molecular weight distribution was observed). After a titanium chloride secondary impregnation (possibly done in presence of an additional Lewis base), activity resumed but polymer properties are once again unchanged. These findings highlight the difficulty to separate the different families of active sites and lead us to propose a cluster organization of titanium active sites. Active sites are composed of titanium clusters having a size distribution at the precatalyst surface, possessing a critical operating size and operating collectively in polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5461–5470, 2008
Preparation of novel acrylamide‐based thermoresponsive polymer analogues and their application as thermoresponsive chromatographic matrices
Authors: Akiyama Yoshikatsu , Shinohara Yasurou , Hasegawa Yukio , Kikuchi Akihiko , Okano Teruo 
Published: July 2008

AbstractNew thermoresponsive polymers based on poly(N‐(N′‐alkylcarbamido)propyl methacrylamide) analogues were designed with increased hydrophobic content to facilitate temperature‐dependent chromatographic separations of peptides and proteins from aqueous mobile phases. These polymer solution exhibited a lower critical solution temperature (LCST) when the alkyl group is methyl, ethyl, isopropyl, propyl, butyl, and isobutyl. However, larger alkyl groups such as hexyl and phenyl were not soluble in aqueous solutions at any temperature. Phase transition temperatures were lower for larger alkyl groups and increased with decreasing polymer molecular weight and concentration in solution. LCST dependence on polymer molecular weight and concentration is more significant compared with well‐studied poly(N‐isopropylacrylamide) (PIPAAm). Partition coefficient (log P) values for N‐(N′‐butylcarbamide)propylmethacrylamide and N‐(N′‐isobutylcarbamide)propyl methacrylamide (iBuCPMA) monomers are larger than that for IPAAm monomer, suggesting higher hydrophobicity than IPAAm. Chromatographic evaluation of poly(N‐(N′‐isobutylcarbamide)propyl methacrylamide) (PiBuCPMA) grafted silica particles in aqueous separations revealed larger k′ values for peptides, insulin, insulin chain B, and angiotensin I than PIPAAm‐grafted silica beads. In particular, k′ values for insulin obtained from PiBuCPMA‐grafted silica separations were much larger than those from PIPAAm‐grafted surface separations, indicating that PiBuCPMA should be more hydrophobic than PIPAAm. These results support the introduction of alkylcarbamido groups to efficiently increase thermoresponsive polymer hydrophobicity of poly(N‐alkylacrylamides) and poly(N‐alkylmethacrylamides). Consequently, poly(N‐(N′‐alkylcarbamido)propyl methacrylamide) analogues such as PiBuCPMA and poly(N‐(N′‐alkylcarbamido)alkylmehacrylamide) are new thermoresponsive polymers with appropriate hydrophobic partitioning properties for protein and peptide separations in aqueous media, depending on selection of their alkyl groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5471–5482, 2008
Highly fluorescent mono‐substituted poly(arylacetylene)s containing tolane chromophores
Authors: Han Chien‐Chung , Balasubramanian Arumugam 
Published: July 2008

AbstractA new class of highly fluorescent mono‐substituted polyarylacetylenes (P1–P3) has been successfully prepared with good yields and high molecular weights from a series of phenylethynylene‐substituted arylacetylenes (M1–M3), using W‐based catalyst. These polymers are readily soluble in common organic solvents (e.g., THF, toluene, and chloroform) and thermally stable up to ∼350 °C. Both 1H NMR and IR studies confirmed that all the monomers were selectively polymerized at the terminal triple bond. The 1H NMR results showed that both P1 and P2 have essentially trans‐polyene backbone structures, while P3 contains significant amounts of both cis‐ and trans‐structures. Coincidently, the photoluminescence (PL) intensity of P3 is also much lower than both P1 and P2. Nevertheless, the PL intensity of P1–P3 are all much higher than that of PPA, suggesting that the introduction of phenylethynylene group to the phenyl rings of PPAs have made the in general nonemissive PPAs to become highly photoluminescent. Most interestingly, although P1 did not contain any substituent group on its tolane pendant group, it is already highly soluble in common organic solvent and emitting blue fluorescence (416 nm) with a reasonably good quantum yield (0.36). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5483–5498, 2008
Effect of Lewis and Brønsted acids on the homopolymerization of acrylates and their copolymerization with 1‐alkenes
Authors: Luo Rong , Chen Ying , Sen Ayusman 
Published: July 2008

AbstractThe first copolymerization of acrylate and methacrylate with nonpolar 1‐alkenes in the presence of Brønsted acids as complexation agents has been reported. The addition of both homogeneous and heterogeneous Brønsted acids resulted in increased monomer conversion and 1‐alkene incorporation. Further, the heterogeneous Brønsted acids can be recycled without loss of activity. A direct correlation exists between the ability of the Lewis or Brønsted acid to bind to the ester group of the acrylate/methacrylate monomer and its ability to promote the copolymerization reaction. For Lewis acids, there is also a direct correlation between the charge/size ratio at the metal center and their ability to promote copolymerizations. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5499–5505, 2008
Synthesis and solution properties of well‐defined comb‐on‐comb graft polymers
Authors: Sun Wei , Yu Fengping , He Junpo , Zhang Chao , Yang Yuliang 
Published: July 2008

AbstractWell‐defined comb‐on‐comb copolymers of styrene, isoprene, and α‐methyl‐styrene are prepared through cascade “grafting‐onto” methods. The polymer main chain is prepared by nitroxide‐mediated radical polymerization while the branches are prepared by anionic polymerization. The “grafting‐onto” approach employs the coupling chemistry of macromolecular anions, such as polystyryllithium, polyisoprenyllithium, or poly(α‐methylstyryl)lithium, toward either benzyl chloride or epoxy ring on precursor backbones. Thus a series of ABA‐, ABB‐, and ABC‐type comb‐on‐comb copolymers are prepared and characterized by gel permeation chromatography equipped with a multi‐angle laser light scattering detector and a viscometer. Unusual “U‐shaped” dependences of radius of gyration, Rg, on molecular weight are observed for comb‐on‐comb products, which are attributable to delayed elution of the densely grafted copolymers from GPC columns. The result also shows that the comb‐on‐comb copolymers exhibit morphologies from hard sphere to cylindrical rod, depending on the length ratio of the main chain to the branches. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5518–5527, 2008
Polymerization of methyl acrylate and as comonomer with ethylene using a bis(imino)pyridine iron(II) chloride/methylaluminoxane catalyst
Authors: Fullana Matthew J. , Miri Massoud J. , Vadhavkar Sameer S. , Kolhatkar Nikhil , Delis Alexander C. 
Published: July 2008

AbstractThis article describes the homopolymerization of methyl acrylate (MA) and its attempted copolymerization with ethylene using three single‐site catalysts. The primary catalyst under investigation is formed from a bis(imino)pyridine iron(II) chloride with methylaluminoxane (1), which is compared with bis(4,5,6,7‐tetrahydro‐1‐indenyl)zirconium dimethyl/tris(pentafluorenyl)borane) (2), and a P,O‐chelated nickel(II) enolate catalyst (3). Catalyst (1) leads to the highest activities exceeding those of catalyst (2) by a magnitude, whereas catalyst (3) results in formation of no polymer. The kinetics of the polymerizations and the effect of the Al/Fe‐ratio and temperature on the activity and molecular weight of the polymers have been determined. In the ethylene/MA copolymerization trials, catalyst (1) produces a blend of the two homopolymers, polymethyl acrylate (PMA) and polyethylene. Remarkably, using catalyst (1) it is possible to produce polymer blends with up to 52% PMA at relatively high activities. The polymerization kinetics has been determined based on the directly measured uptake of ethylene during the runs. NMR spectroscopy, DSC and GPC measurements have been used as efficient methods to prove that polymer blends instead of true copolymers were formed. Finally, some conclusions about the polymerization mechanism will be drawn. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5542–5558, 2008
Synthesis and characterization of asymmetric centipede‐like copolymers with two side chains at each repeating unit via ATRP and ring‐opening polymerization
Authors: Shi Gang‐Yin , Zou Peng , Pan Cai‐Yuan 
Published: July 2008

AbstractA series of well‐defined centipede‐like copolymers with poly(glycidyl methacrylate) (PGMA) as main chain and poly(L‐lactide) (PLLA) and polystyrene (PSt) as side chains have been synthesized successfully by combination of ring‐opening polymerization and atom transfer radical polymerization (ATRP). The synthetic process includes three steps. (1) Synthesis of PGMA via ATRP; (2) preparation of macroinitiator with one bromine group and a hydroxyl group at every GMA unit of PGMA; (3) ring‐opening polymerization of LLA and ATRP of St to obtain the asymmetric centipede‐like copolymers. The number–average degrees of polymerization of PGMA backbone, PLLA and PSt side chains were determined by 1H‐NMR spectra, and the molecular weights of the resultant intermediates and centipede‐like copolymers were measured by gel permeation chromatography. The molecular weight distributions were narrow and the molecular weights of both the backbone and the side chains were controllable. The thermal behavior of the centipede‐like copolymers was investigated by differential scanning calorimeter. With the increase of PSt side chain length, the glass transition temperature of PLLA side chains shifted to high temperature, and crystallization ability of PLLA side chains became poor. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5580–5591, 2008
Carbazolevinylene‐based polymers and model compounds with oxadiazole and triphenylamine segments: Synthesis, photophysics, and electroluminescence
Authors: Vellis Panagiotis D. , Mikroyannidis John A. , Cho Min Ju , Choi Dong Hoon 
Published: July 2008

AbstractTwo new soluble alternating carbazolevinylene‐based polymers POXD and PTPA as well as the corresponding model compounds MOXD and MTPA were synthesized by Heck coupling. POXD and MOXD contained 2,5‐diphenyloxadiazole segments, while PTPA and MTPA contained triphenylamine segments. All samples displayed high thermal stability. The polymers had higher glass transition temperature (Tg) than their corresponding model compounds. The samples showed absorption maximum at 364–403 nm with optical band gap of 2.62–2.82 eV. They emitted blue‐green light with photoluminescence (PL) emission maximum at 450–501 nm and PL quantum yields in THF solution of 0.15–0.36. The absorption and the PL emission maxima of PTPA and MTPA were blue‐shifted as compared to those of POXD and MOXD. The electroluminescence (EL) spectra of multilayered devices made using four materials exhibited bluish green emissions, which is well consistent with PL spectra. The EL devices made using poly(vinyl carbazole) doped with MOXD and MTPA as emitting materials showed luminances of 12.1 and 4.8 cd m−2. POXD and PTPA exhibited 25.4, and 96.3 cd m−2, respectively. The polymer containing the corresponding molecules in the repeating group showed much higher device performances. Additionally, POXD and MOXD exhibited better stability of external quantum efficiency (EQE) and luminous efficiency with current density resulting from enhancing the electron transporting properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5592–5603, 2008
Synthesis and self‐assembly of poly(styrene)‐b‐poly(N‐vinylpyrrolidone) amphiphilic diblock copolymers made via a combined ATRP and MADIX approach
Authors: Hussain H. , Tan B. H. , Gudipati C. S. , Liu Y. , He C. B. , Davis T. P. 
Published: July 2008

AbstractAmphiphilic diblock copolymers of polystyrene (PS) and poly(N‐vinylpyrrolidone) (PNVP) were prepared by a combination of ATRP and MADIX. Well‐defined PS with bromine end group was synthesized by ATRP in bulk at 110 °C using (1‐bromoethyl) benzene as an initiator. The Br‐ end group was then converted to xanthate as verified by1H NMR spectroscopy, elemental analysis, and UV‐spectroscopy. PS‐b‐PNVP copolymers were produced by MADIX of NVP in bulk at 60 °C using PS‐xanthate as a macro‐chain transfer agent and the kinetics of polymerization were investigated. The structures of PS‐b‐PNVP were characterized using GPC and1H NMR. Amphiphilic PS‐b‐PNVP could form spherical micelles with PS cores and PNVP shells in aqueous solution as confirmed by1H NMR and laser light scattering (LLS). The values of critical micelle concentration of PS‐b‐PNVP and the average aggregation number of PS‐b‐PNVP in the micelles were measured using pyrene as a probe and static LLS, respectively. The aggregation number increases concomitantly with temperature (10–50 °C), but the hydrodynamic radius of the micelles remains almost constant over the same temperature range, which may indicate shell dehydration at a higher temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5604–5615, 2008
Synthesis and characterization of PNIPAM‐b‐(PEA‐g‐PDEA) double hydrophilic graft copolymer
Authors: Feng Chun , Shen Zhong , Gu Lina , Zhang Sen , Li Litao , Lu Guolin , Huang Xiaoyu 
Published: July 2008

AbstractA series of well‐defined double hydrophilic graft copolymers, consisting of poly(N‐isopropylacrylamide)‐b‐poly(ethyl acrylate) (PNIPAM‐b‐PEA) backbone and poly(2‐(diethylamino)ethyl methacrylate) (PDEA) side chains, were synthesized by successive atom transfer radical polymerization (ATRP). The backbone was firstly prepared by sequential ATRP of N‐isopropylacrylamide and 2‐hydroxyethyl acrylate at 25 °C using CuCl/tris(2‐(dimethylamino)ethyl)amine as catalytic system. The obtained diblock copolymer was transformed into macroinitiator by reacting with 2‐chloropropionyl chloride. Next, grafting‐from strategy was employed for the synthesis of poly(N‐isopropylacrylamide)‐b‐[poly(ethyl acrylate)‐g‐poly(2‐(diethylamino)ethyl methacrylate)] (PNIPAM‐b‐(PEA‐g‐PDEA)) double hydrophilic graft copolymer. ATRP of 2‐(diethylamino)ethyl methacrylate was initiated by the macroinitiator at 40 °C using CuCl/hexamethyldiethylenetriamine as catalytic system. The molecular weight distributions of double hydrophilic graft copolymers kept narrow. Thermo‐ and pH‐responsive micellization behaviors were investigated by fluorescence spectroscopy, 1H NMR, dynamic light scattering, and transmission electron microscopy. Unimolecular micelles with PNIPAM‐core formed in acidic environment (pH = 2) with elevated temperature (≥32 °C); whereas, the aggregates turned into vesicles in basic surroundings (pH ≥ 7.2) at room temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5638–5651, 2008
Structural characterization of radiation‐grafted block copolymer films, using SANS technique
Authors: Mortensen Kell , Gasser Urs , Gürsel Selmiye Alkan , Scherer Günther G. 
Published: July 2008

AbstractWe report small‐angle neutron scattering studies of grafted copolymer films of perfluorinated poly(ethylene propylene), FEP, base polymer and polystyrene, PS, grafted blocks. The films show highly anisotropic scattering patterns, revealing nematic‐like ordering of the crystalline domain structure as a consequence of the processing conditions. Upon grafting, the styrene swells the amorphous domains in the copolymer formation. For styrene content beyond roughly 15%, the amorphous regimes increase on the cost of crystalline domains. To stabilize the rather well‐defined domain structure already given by the original FEP base material, the samples need to be cross‐linked. Without cross‐linking, the nanometer length scale domains vanish, and some large scale structure takes over, likely driven by the immiscibility between FEP and PS. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1660–1668, 2008