A facile route to ureidopyrimidinone‐functionalized polymers via RAFT

Three new ureidopyrimidinone(UPy)‐functionalized chain‐transfer agents (CTAs) have been synthesized for use in reversible addition‐fragmentation chain transfer (RAFT) polymerization. These UPy‐CTAs are able to polymerize a wide variety of vinyl monomers to yield UPy‐functionalized polymers, including homopolymers, block copolymers, and amphiphilic block copolymers. These polymers have been characterized via ¹H and ¹³C NMR spectroscopy, gel permeation chromatography (GPC), UV/visible spectroscopy and differential scanning calorimetry (DSC) to demonstrate end‐group fidelity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

高分子体系的溶剂吸附平衡预测

通过考察芳香族溶剂和聚丙烯酸酯混合过程内聚能和混合体积的变化,阐明剩余体积对高分子溶液体系相平衡的影响,在理论上比较UNIFAC-FV和GCLF-EOS模型。使用石英弹簧法测定25℃下苯、甲苯和乙苯在聚丙烯酸甲酯、聚丙烯酸丁酯和聚丙烯酸十二酯中的吸附曲线,分别用以上数学模型对其进行预测,由于GCLF-EOS模型以状态方程式作为基础,能够正确反映高分子溶液中分子间相互作用和剩余体积变化行为,模型预测结果和实验值基本一致。     

Linear Polymers from Diene Monomers by the Cyclic Polymerization Mechanism. XI. Polyphosphonium Salts via Cyclopolymerization

A wide variety of diunsaturated phosphonium salts have been synthesized in order to determine whether or not such structures undergo cyclopolymerization. As intermediates for these monomers, a number of previously unreported unsaturated phosphines have been prepared and characterized. Polymerization studies using a wide variety of free radical initiating conditions led to polymers in those cases which were predicted to undergo cyclopolymerization leading to five-, six-, or seven-membered rings with one exception. The properties of the polymers are consistent with the cyclopolymerization mechanism. The conversion of poly(diallyldiphenylphosphonium bromide) to polfidiallyldiphenylphosphine oxide) offers additional evidence for cyclopolymerization. Di-3-butenyldiphenylphosphonium bromide, a monomer functionally capable of forming a polymer containing an eight-membered ring, did not polymerize. Divinylphenylphosphine was found to undergo copolymerization with acrylonitrile in accordance with the cyclo-copolymerization mechanism.     

Synthesis and Characterization of Novel Amphiphilic Polymers as Drug Delivery Nano Carriers

Polymer nano-particles have been widely investigated in the last decade due to a variety of potential applications. In particular, polymers which can self assemble into micellar nano-particles can be effectively used as vehicles for drug delivery. Considerable efforts are underway to develop better drug delivery nano carriers for high drug loading capacity for a wide variety of bioactive compounds. In this study, several new polymers were synthesized in bulk (solventless condition) by a chemo-enzymatic methodology using Candida antarctica lipase B (Novozyme 435) and molecular sieves (MS). The synthesized polymers demonstrated high drug loading capacity and the potential to encapsulate drugs which are poorly soluble in aqueous solvents.     

History of Organometallic Polymers

In the last 20 years a wide variety of new types of polymers has been prepared containing metals as an integral part of the polymer backbone. This paper summarizes deveopments in the following major areas: vinylic polymers, including vinyl metal-locene derivatives and vinylic tin monomers; condensation polymers; polyorganophosphazenes; coordination polymers; mixed valence polymers with electrical conductivity such as (SN)_x, polyacetylene and polyphenylene; stacked polymers such as platinum blue, polyphthalocyanines, and TTF-TCNQ. The methods of synthesis and potential applications of these materials in areas such as catalysis, elastomers with low and high temperature stability, metallic conductors, semiconductors, bacteriacides, fungicides, and cancer chemotherapeutic agents are discussed.     

Facile postpolymerization end‐modification of RAFT polymers

One‐pot methods for the end‐group postpolymerization modification of reversible addition fragmentation chain transfer (RAFT) derived polymers were investigated. Dithioester‐terminated polymers were transformed into ω‐functionalized polymers through conjugate addition of a variety of acrylates with an intermediate thiol. These methods provide a versatile means of introducing a variety of functionalities onto the polymer terminus, while simultaneously removing the residual dithiobenzoate group. A series of functionalized polymethylmethacrylate‐b‐polystyrene (PMMA‐b‐PS) polymers were synthesized utilizing the developed methods to probe the effect of charged end groups on diblock copolymer phase separation in thin films. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 346–356, 2009     

Étude thermodynamique du système compatible polyfluorure de vinylidène-polyméthacrylate d'éthyle par chromatographie gaz-liquide

The thermodynamics of interaction between poly(ethyl methacrylate) and poly(vinylidene fluoride) have been studied by gas-liquid chromatography on their homogeneous blends (40 < PVDF < 80% by weight) in the liquid state (t > 140°C) using a variety of probes covering a wide range of polarity and of affinity for the polymers. The average and most representative interaction parameter χ₂₃′ (Flory-Huggins) is estimated as −0.32 ± 0.09, showing only slight sensitivity to temperature between 160 and 200°C and composition of the blend. The purely interactional χ₂₃ parameter (Prigogine-Flory-Patterson) is strongly negative (χ₂₃ = −6.5 J/cm³) as a result of dipolar and hydrogen bond interactions between the polymers.     

Alkyl modified anionic siloxanes as pseudostationary phases for electrokinetic chromatography. I. Synthesis and characterization

Anionic water soluble siloxane polymers have been synthesized and characterized for electrokinetic chromatography. Siloxane polymers are of interest in electrokinetic chromatography because of the wide variety of chemistries that can be developed based on these backbones, including much of the stationary phase chemistry developed in the last 30 years. The siloxanes in this study have a sulfonate functional group. The siloxanes have different length alkyl chains (C8, C12, C18) attached to the backbone in differing densities. The methylene selectivity generally increases with increasing alkyl chain length and with increasing alkyl chain density. The electrophoretic mobility appears to pass through a maximum as more alkyl chain is added to the siloxane backbone. The efficiency also would seem to pass through a maximum as more alkyl chain is added. The chemical selectivities of the siloxane polymers are very different from sodium dodecyl sulfate but are similar to each other.     

Effect of diisocyanate nature on the properties of cyclolinear polyureas containing azacrown ether groups

New cyclolinear polyureas based on a crown-containing diamine—1,10-diaza-18-crown-6—and organic diisocyanates of different natures (aliphatic, aromatic, and alicyclic compounds) and an oligomeric diisocyanate have been synthesized. It has been found that, unlike most polyureas, azacrown-containing polymers are soluble in a wide variety of organic solvents. The calorimetric and mechanical properties of these polymers in dry and equilibrium-swollen states have been studied. It has been shown that the basic characteristics of these cyclolinear systems can be tailored by varying the nature of the diisocyanate used.     

Synthesis and energy-transfer properties of hydrogen-bonded oligofluorenes

A set of fluorene oligomers has been synthesized by stepwise palladium-catalyzed (Suzuki) couplings of fluorene monomers. Ureidopyrimidinones (UPy), functional groups that can dimerize via quadruple hydrogen bonds, were attached to both ends of the oligofluorenes. The resulting bis-UPy-terminated oligomers self-assemble into supramolecular chain polymers. For comparison, oligofluorenes of the same oligomer lengths but without terminal hydrogen-bonding groups were synthesized. Chains of hydrogen-bonded fluorenes can be simply endcapped by a variety of chain stoppers, molecules that have one UPy group. In this manner, we have endcapped the hydrogen-bonded fluorene chains with either oligo(p-phenylenevinylene) or perylene bisimide. Energy-transfer experiments in solution and the solid state demonstrate that oligofluorenes can donate energy to a variety of energy acceptors, but that this energy transfer occurs most effectively when the donor fluorene is hydrogen-bonded to the acceptor.     

Methods for the synthesis of uniform polymers

The difficulties encountered in the preparation of polymers that are uniform chemically, structurally, and in their molecular weight are due mainly to the wide variety of possible polymers. This arcticle gives a review of attempts to synthesize homogeneous polymers by chain reactions and by stepwise synthesis. Syntheses on templates are extremely important in living cells; methods have recently been found for syntheses of this type that are independent of natural processes. Uniform polymers can also be obtained by reactions on existing polymers. In replicating polymers, this in principle requires the modification of only one polymer molecule.     

Crystalline Hetero‐Stereocomplexed Polycarbonates Produced from Amorphous Opposite Enantiomers Having Different Chemical Structures

Stereocomplexation is the stereoselective interaction between two opposite enantiomeric polymers through an interlocked orderly assembly. Most studies focus on the stereocomplex formation from the crystalline opposite enantiomers having the identical structure; nevertheless, rare examples were reported regarding the crystalline stereocomplexes from enantiomeric polymers having different chemical structures. Herein we show a strategy for polymer orderly assembly through the formation of crystalline hetero‐stereocomplexed polymeric materials by the cocrystallization of amorphous isotactic polycarbonates with different chemical structures and opposite configurations. The behaviors in the crystalline state are significantly different from that of the component enantiomeric polymers or their homo‐stereocomplexes. This study is expected to open up a new way to prepare various semicrystalline materials having a wide variety of physical properties and degradability.     

Structure,energy spectra and magnetic properties of poly(m-aniline)s

The energy spectra and magnetic properties of a large class of one-dimensional poly(m-aniline)s (PMA) and further model polymers are investigated theoretically. The band structure of those PMA's which are aza-analogs of the alternant non-classical (non-Kekulé) hydrocarbons (polymers) is characterized by a wide gap in which there is a narrow half-filled band (HFB). The different contributions to the effective spin exchange between the unpaired electrons in the HFB: Coulomb (Hund), kinetic and indirect exchange interactions are calculated. While it has been shown earlier that PMA exhibits a net spin exchange of ferromagnetic nature, this approach enables a detailed understanding of the influence of substituents on the nitrogen centers and changes in the aromatic bridging unit. The ferromagnetic nature of the spin coupling in the singly bridged PMA models therebye prevails independent of the structural changes. The HFB width of those PMA's which are derivatives (aza-analogs) of ladder-type non-alternant hydrocarbons is very large and the Wannier functions are delocalized. For this group of polymers the delocalized, non-magnetic state is favored and, therefore, they may be good candidates for testing electrical conduction.     

Synthesis and characterization of new photosensitive poly (oxyaryleneoxydisilane)s from 1,2-bis (diethylamino) tetramethyldisilane and various bisphenols

A new class of polymers containing a photosensitive disilane unit in the polymer main chain with inherent viscosities between 0.1 and 0.59 dL/g was prepared by the melt polycondensation of 1,2-bis (diethylamino) tetramethyldisilane and various bisphenols. The polymers were characterized by UV, IR, ¹H-NMR, and elemental analysis. Poly(oxyaryleneoxydisilane)s were soluble in a variety of common organic solvents and have a wide range of glass transition temperatures varying between ?65 and 135°C, depending on the arylene structure. Most of the polymers were stable up to 350°C in both air and nitrogen atmospheres. The inherent viscosity of the polymer containing the 1,6-napthalene unit decreased drastically upon UV light irradiation, indicating its photodegradation.     

Stannylated polynorbornenes as new reagents for a clean Stille reaction

New functionalized polynorbornenes have been obtained in good yields by vinylic copolymerization of norbornene with a (norbornenyl)SnBu(2)Cl monomer, catalyzed by [Ni(C(6)F(5))(2)(SbPh(3))(2)]. Subsequent functionalization produces a wide variety of polymers with different --SnBu(2)R groups (R=aryl, vinyl, alkynyl). The polymers can be used as R-transfer reagents in Stille couplings, thereby providing easy workup and separation of the polymeric tin byproducts from the coupling products. Tin contents of around 0.05 wt % are found in the Stille products. The stannylated polymers can be recycled and reused with good efficiency.     

Tandem transition metal catalyzed isomerization and cationic polymerization

A wide variety of mono-, di- and multifunctional allyl ethers and related compounds are readily polymerized using a newly discovered polymerization reaction which has been termed: a transition metal-catalyzed tandem isomerization and cationic polymerization. Employing dicobalt octacarbonyl in combination with organosilanes, the polymerization of these monomers takes place rapidly to give high molecular weight polymers.     

Reaction of functionalised thiols with oligoisobutenes via free-radical addition.: Some new routes to thermoplastic crosslinkable polymers

The functionalisation of vinylidene (isopropenyl) terminated oligoisobutenes (polyisobutenes; PIB) with several thiols has been realised in the presence of free-radical generators. Oxygen (air) is a significant accelerator for this reaction and in some cases, alone, is sufficient to cause the reaction to occur. Free-radicals were generated from peroxydicarbonates, AIBN or UV irradiation. The reaction is of an anti-Markovnikov type with the RS-function adding to the vinylidene CH₂ group selectively in the presence of more substituted olefin groups in commercial PIB. A variety of thiols has been investigated and the synthesis of elastomeric polymers resulting from the hydrolysis and condensation of a trialkoxysilane coupled to PIB via a sulphide link has been demonstrated. The synthesis of comb-like polymers made by the addition of PIB to poly(mercaptopropyl methylsiloxane) has been achieved in a way to leave some non-reacted thiol functions available for crosslinking. A perfluoroalkyl thiol modified PIB shows a significant reduction in surface tension compared to the starting PIB polymer.     

Synthesis of asymmetric star-branched polymers consisting of three or four different segments in composition by means of living anionic polymerization with a new dual-functionalized 1,1-bis(3-chloromethylphenyl)ethylene

A series of four-armed A₂BC, AB₂C, and ABC₂ asymmetric star-branched polymers with a three-component system, the A, B, and C segments of which are polystyrene, polyisoprene, and poly(4-trimethylsilylstyrene), respectively, have been successfully synthesized with a methodology based on living anionic polymerization with dual-functionalized 1,1-bis(3-chloromethylphenyl)ethylene ( 1 ). These star-branched polymers have well-defined architectures and precisely controlled chain lengths, as confirmed by size exclusion chromatography, ¹H and ¹³C NMR, vapor pressure osmometry, and static light scattering analyses. A simple and convenient one-pot process for star-branched polymer synthesis is an additional advantage of this methodology. One problem to be solved is that the synthetic route is limited in some cases by the inherently low reactivity of polyisoprenyllithium toward the 1,1-diphenylethylene functionality of in-chain-functionalized polymers. A new four-armed ABCD star-branched polymer, the A, B, C, and D segments of which are polyisoprene, poly(4-methoxystyrene), polystyrene, and poly(4-trimethylsilylstyrene), could also be synthesized through the extension of the methodology using 1 to a four-component system. The successful results strongly demonstrate the synthetic versatility and potential of this methodology for a wide variety of well-defined asymmetric star-branched polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4535–4547, 2004     

Synthesis and properties of poly(acrylamide)s containing both long chain alkyl groups and phosphatidylcholine analogues in the side chains

A series of new phospholipid analogous acrylamide monomers ( 4a–e ) containing long alkyl chains as hydrophobic groups and containing phosphatidylcholine analogues as hydrophilic group were synthesized in high yields. The homopolymerizations and copolymerization ( 4b with 4e ) were carried out in the presence of a radical initiator. The structures and thermal properties of these polymers were investigated by x-ray diffraction analysis, DSC, and polarizing microscopy measurements. It has been revealed that these homopolymers ( 5b, 5c , and 5d ) which bear saturated long-hydrocarbon chains in the side chains exhibited not only orderly stacked bilayer structures at room temperature but also clear liquid crystalline behavior within a wide temperature range. The viscosity behavior of all polymers was found similar to usual polyelectrolytes in porlar solvent. The polymers obtained were also characterized by ¹H-NMR, IR, and melting point, respectively. © 1996 John Wiley & Sons, Inc.