Synthesis of ultra high molecular weight poly(dimethyldiallyl ammonium chloride)

In the study we reported the synthesis of poly-(dimethyldiallyl ammonium chloride) (PDMDAAC) with ultra high molecular weight. The polymerization method consists in the following: the ultra-high purity monomer synthesized in lab was used as the raw material, and APS as the initiator. APS was added in a lump and the polymerization temperature was increased stepwise to complete the polymerization gradually in 9 h reaction time. The maximum intrinsic viscosity ([η]) of PDMDAAC reached 3.66 dL g^–1 at a monomer conversion rate (Conv) of 96.71%. The structure and properties of PDMDAAC were characterized using FTIR, NMR, GPC-MALLS, and DTA-TG. The effects of polymerization conditions, such as the polymerization temperature, m(DMDAAC), m(APS): m(DMDAAC), and m(Na₄EDTA): m(DMDAAC), on the [η] and Conv of products were investigated. Meanwhile, the effects of the monomer purity on the [η] of products were compared. The results showed that the types and amount of impurities in monomer solution are two key factors, which affect the polymerization and, thus, the molecular weight of products.     

ε‐Caprolactone/ZnCl2 complex formation: Characterization and ring‐opening polymerization mechanism

ε‐Caprolactone (ε‐CL) has been mixed with ZnCl₂ at different mol ratios. The resulting complex was characterized through ¹H and ¹³C NMR spectroscopy in bulk and in solutions, differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), and optical microscopy. Ring‐opening polymerization of ε‐caprolactone [M] using ZnCl₂ as an initiator [I] at different monomer/initiator ratios has been successfully performed in xylene. The molecular weight of poly(ε‐caprolactone) (PCL) as measured by gel permeation chromatografy (GPC) was found to depend linearly on the [M]/[I] ratio. Theoretical calculations were carried out to understand the geometry of the complex and the operating ring‐opening mechanism. Both experimental and computational results and the presence of methylene–chloride end group, confirmed by NMR, are in agreement with a coordination–insertion mechanism for the ring‐opening polymerization proposed in this article. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1355–1365, 2000     

Cationic polymerization of vinyl ether with a benzoate pendant: The formation of long‐lived polymers and the identification of side reactions

The cationic polymerization of 2‐[4‐(methoxycarbonyl)phenoxy] ethyl vinyl ether, a vinyl ether with a benzoate pendant, was carried out with an HCl/ZnCl₂ initiating system in methylene chloride at −15 °C. The polymerization proceeded with living/long‐lived propagating species to produce polymers with controlled molecular weights and relatively narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight ≤ ∼1.4), despite the formation of a small amount of oligomeric products during the polymerization. The structural analysis showed that the lowest molecular weight oligomer had the structure CH₃CH(OCH₂CH₂OC₆H₄COOCH₃)OCH₂CH₂OC₆H₄COOCH₃. The oligomer was formed by the reaction of the monomeric propagating species with the alcohol produced by the side reaction of the active species with water as an impurity during the early stage of polymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4362–4372, 2000     

Effect of pH on radical polymerization of butadiene 1-carboxylic acid in aqueous solutions

Radical polymerization of butadiene 1-carboxylic acid (Bu-1-Acid) was carried out in aqueous solutions at 50°C with ammonium persulfate (APS) as an initiator. Kinetic studies led to the rate equation, R_p = k[APS]^1/2 [Bu-1-Acid]¹ at pH 6.8. The overall activation energy for the polymerization was 16.0 kcal/mole. The polymerization rate R_p of Bu-1-Acid decreased with an increase of pH in the range 2.4–6.8 and increased with an increase of pH in the range 6.8–8.4. Moreover, in the pH range 8.4–13, the rate of polymerization was not affected by the pH of the system. In copolymerization with acrylonitrile, the trends of changes in the monomer reactivity ratios r₁, r₂ and Q-e values caused by changes in pH were similar to trends found in homopolymerization described above. In addition, it was observed that the resultant polymer was extended in alkaline solution and contracted in acidic solution.     

Controlled polymerization of 2‐(diethylamino)ethyl methacrylate and its block copolymer with N‐isopropylacrylamide by RAFT polymerization

Poly(2‐(diethylamino)ethyl methacrylate) (PDEAEMA) homopolymers with low polydispersities were synthesized by reversible addition fragmentation chain transfer (RAFT) radical polymerization. The performances of two chain transfer agents, 2‐cyanoprop‐2‐yl dithiobenzoate and 4‐cyanopentanic acid dithiobenzoate (CPADB), were compared. It was found that the polymerization of 2‐(diethylamino) ethyl methylacrylate was under good control in the presence of CPADB with 4,4′‐azobis(4‐cyanopentanoic acid) (ACPA) as initiator in 1,4‐dioxane at 70 °C. The kinetic behaviors were investigated under different CPADB/ACPA molar ratios. A long polymerization inhibition period was observed at high [CPADB]/[ACPA] ratio. The influences of [CPADB]/[ACPA] ratio, monomer/[CPADB] ratio, and temperature were studied with respect to monomer conversion, molecular weight control, and polydispersity index (PDI). The PDI decreased from 1.21 to 1.12, as the CPADB/ACPA molar ratio changed from 2 to 10. The molecular weight of PDEAEMA could be controlled by monomer/CPADB molar ratio. The control over MW and PDI was improved as the temperature increased from 60 to 70 °C; however, an additional increase to 80 °C led to a loss of control. Using PDEAEMA macroRAFT agent, pH/thermo double‐responsive block copolymers of PDEAEMA and poly(N‐isopropylacrylamide) (PDEAEMA‐b‐PNIPAM) with narrow polydispersity (PDI, 1.24) were synthesized. The lower critical solution temperature of PDEAEMA‐b‐PNIPAM block copolymer depended on the environmental pH. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3294–3305, 2008     

Morphology and temperature responsiveness–swelling relationship of poly(N‐isopropylamide–chitosan) copolymers and their application to drug release

Poly [N‐isopropylacrylamide (NIPAAm)–chitosan] crosslinked copolymer particles were synthesized by soapless emulsion copolymerization of NIPAAm and chitosan. An anionic initiator [ammonium persulfate (APS)] and a cationic initiator [2,2′‐azobis(2‐methylpropionamidine)dihydrochloride (AIBA)] were used to initiate the reaction of copolymerization. The chitosan–NIPAAm copolymer synthesized by using APS as the initiator showed a homogeneous morphology and exhibited the characteristic of a lower critical solution temperature (LCST). The copolymer synthesized by using AIBA as an initiator showed a core–shell morphology, and the characteristic of LCST was insignificant. The LCST of the chitosan–NIPAAm copolymer depended on the morphology of the copolymer particles. In addition, the chitosan–NIPAAm copolymer particles were processed to form copolymer disks. Then, the effect of various variables such as the chitosan/NIPAAm weight ratio, the concentration of crosslinking agent, and the pH values on the swelling ratio of chitosan–NIPAAm copolymer disks were investigated. Furthermore, caffeine was used as the model drug to study the characteristics of drug loading of the chitosan–NIPAAm copolymer disks. Variables such as the chitosan/NIPAAm weight ratio and the concentration of the crosslinking agent significantly influenced the behavior of caffeine loading. Two factors (pore size and swelling ratio) affected the behavior of caffeine release from the chitosan–NIPAAm copolymer disks. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3029–3037, 2004     

Sn(OTf)2 and Sc(OTf)3: Efficient and versatile catalysts for the controlled polymerization of lactones

A general and novel method for the controlled synthesis of aliphatic polyesters is presented. The evaluation of stannous (II) trifluoromethane sulfonate [Sn(OTf)₂] and scandium (III) trifluoromethane sulfonate [Sc(OTf)₃] as catalysts for the ring‐opening polymerization (ROP) of various lactones is described as a route to polyesters under mild and highly selective polymerization conditions. Size exclusion chromatograms of poly(ϵ‐caprolactone) initiated from ethanol in the presence of either Sn(OTf)₂ or Sc(OTf)₃ demonstrate the facile synthesis of narrowly dispersed products. Predictable molecular weights, typical of a living or controlled polymerization, were obtained with high yields. These catalysts are versatile and applicable toward the ROP of other cyclic (di)esters, including β‐butyrolactone, which produces the synthetic analogue of the biopolymer poly(β‐hydroxybutyrate). © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2067–2074, 2000     

R‐RAFT approach for the polymerization of N‐isopropylacrylamide with a star poly(ε‐caprolactone) core

Reversible addition‐fragmentation chain transfer (RAFT) polymerization is a more robust and versatile approach than other living free radical polymerization methods, providing a reactive thiocarbonylthio end group. A series of well‐defined star diblock [poly(ε‐caprolactone)‐b‐poly(N‐isopropylacrylamide)]₄ (SPCLNIP) copolymers were synthesized by R‐RAFT polymerization of N‐isopropylacrylamide (NIPAAm) using [PCL‐DDAT]₄ (SPCL‐DDAT) as a star macro‐RAFT agent (DDAT: S‐1‐dodecyl‐S′‐(α, α′‐dimethyl‐α″‐acetic acid) trithiocarbonate). The R‐RAFT polymerization showed a controlled/“living” character, proceeding with pseudo‐first‐order kinetics. All these star polymers with different molecular weights exhibited narrow molecular weight distributions of less than 1.2. The effect of polymerization temperature and molecular weight of the star macro‐RAFT agent on the polymerization kinetics of NIPAAm monomers was also addressed. Hardly any radical–radical coupling by‐products were detected, while linear side products were kept to a minimum by careful control over polymerization conditions. The trithiocarbonate groups were transferred to polymer chain ends by R‐RAFT polymerization, providing potential possibility of further modification by thiocarbonylthio chemistry. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of poly(chitosan‐N‐isopropylacrylamide) complex particles with the method of soapless dispersion polymerization

Crosslinked poly(chitosan‐N‐isopropylacrylamide) [poly(NIPAAM‐chitosan)] complex particles were successfully synthesized with the method of soapless dispersion polymerization. The anionic initiator ammonium persulfate (APS) and the cationic initiator 2,2′‐azobis(2‐methylpropionamidine) dihydrochloride (AIBA) were used to initiate the copolymerization. The poly(NIPAAM‐chitosan) copolymer particles synthesized with APS as the initiator had a homogeneous morphology, whereas the copolymer particles synthesized with AIBA as the initiator showed a core–shell morphology. In addition, various variables such as the particle size, reaction rate, and ζ potential were taken into account. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2053–2063, 2003     

Nonisothermal crystallization behavior of SPS/APS blends

The nonisothermal crystallization behavior of syndiotactic polystyrene (SPS)/atactic polystyrene (APS) blends was studied with differential scanning calorimetry to investigate the effects of APS on the crystallization behavior of SPS. Polarized optical microscopy and wide‐angle X‐ray diffractometry were also used to observe the morphology of the SPS crystalline structure. From a cyclic heating/cooling temperature program, we obtained found that APS retarded the crystallization (and recrystallization) of SPS and made the crystal less perfect, but the ultimate crystallinity of SPS did not change with the addition of APS. We also observed that APS was disposed in the interfibrillar region of SPS spherulites and did not change the crystalline form of SPS. This result will be helpful for improving SPS applications through blending with rubber‐toughened APS. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 3001–3008, 2000     

Dispersion polymerization of pyrrole using ethylhydroxy-ethylcellulose as a stabilizer

Oxidative polymerization of pyrrole has been studied using FeCl₃ or (NH₄)₂S₂O₈ (APS) as oxidant, ethylhydroxyethylcellulose (EHEC) as a steric stabilizer and water or aqueous ethanol as the dispersion medium. Transmission electron micrographic images of the particles from the as-prepared dialysed dispersions in aqueous ethanol show small as well as large particles (about a decade larger) when FeCl₃ is used as the oxidant but only large particles when APS is used as the oxidant. Small particles are not found when the dispersions are prepared in water, irrespective of the oxidant used. The particle size decreases with an increase in molecular weight of the stabilizer for the same stabilizer concentration. The minimum amount of stabilizer required to support dispersion polymerization decreases upon increasing the alcohol content of the medium. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3723–3729, 1999     

Polymerization mechanism for in situ supported metallocene catalysts

The polymerization of ethylene was carried out with a novel in situ supported metallocene catalyst that eliminated the need for a supporting step before polymerization. In the absence of trimethyl aluminum (TMA), in situ supported Et[Ind]₂ZrCl₂ was not active, but the addition of TMA during polymerization activated the catalyst. Et[Ind]₂Zr(CH₃)₂ was active even in the absence of TMA, whereas the addition of TMA during polymerization enhanced the catalytic activity. The polymerization‐rate profiles of the in situ supported metallocene catalysts did not show rate decay as a function of time. A polymerization mechanism for the in situ supported metallocene catalysts is proposed for this behavior. During polymerization, the in situ supported metallocene catalysts may deactivate, but homogeneous metallocene species present in the reactor may form new active sites and compensate for deactivated sites. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 462–468, 2000     

Facile synthesis of N‐vinylimidazole‐based hydrogels via frontal polymerization and investigation of their performance on adsorption of copper ions

We report a new facile strategy for quickly synthesizing pH sensitive poly(VI‐co‐HEA) hydrogels (VI = N‐vinylimidazole; HEA = 2‐hydroxyethyl acrylate) by frontal polymerization. The appropriate amounts of VI, HEA, and ammonium persulfate (APS)/N,N,N′,N′‐tetramethylethylenediamine (TMEDA) couple redox initiator were mixed together at ambient temperature in the presence of glycerol as the solvent medium. Frontal polymerization (FP) was initiated by heating the upper side of the mixture with a soldering iron. Once initiated, no further energy was required for the polymerization to occur. The dependence of the front velocity and front temperature on the VI/HEA weight ratios were investigated. The pH sensitive behavior, morphology, and heavy metal removal study of poly(VI‐co‐HEA) hydrogels prepared via FP were comparatively investigated on the basis of swelling measurements, scanning electron microscopy, and inductively coupling plasma spectrometer. Results show that the poly(VI‐co‐HEA) hydrogels prepared via FP exhibit good pH sensitivity and adsorption capacity. The FP can be exploited as an alternative means for synthesis of pH sensitive hydrogels in a fast and efficient way. The as‐prepared hydrogels can be applied to remove heavy metals. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4005–4012, 2010     

Atom transfer radical polymerization of styrene and methyl methacrylate catalyzed by FeCl2/iminodiacetic acid

The atom transfer radical polymerization of styrene and methyl methacrylate with FeCl₂/iminodiacetic acid as the catalyst system in bulk was successfully implemented at 70 and 110 °C, respectively. The polymerization was controlled: the molecular weight of the resultant polymer was close to the calculated value, and the molecular weight distribution was relatively narrow (weight‐average molecular weight/number‐average molecular weight ∼ 1.5). Block copolymers of polystyrene‐b‐poly(methyl methacrylate) and poly(methyl methacrylate)‐b‐poly(methyl acrylate) were successfully synthesized, confirming the living nature of the polymerization. A small amount of water added to the reaction system increased the reaction rate and did not affect the living nature of the polymerization system. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4308–4314, 2000     

Influence of the catalyst and polymerization conditions on the long‐chain branching of metallocene‐catalyzed polyethenes

A study was made on the effects of polymerization conditions on the long‐chain branching, molecular weight, and end‐group types of polyethene produced with the metallocene‐catalyst systems Et[Ind]₂ZrCl₂/MAO, Et[IndH₄]₂ZrCl₂/MAO, and (n‐BuCp)₂ZrCl₂/MAO. Long‐chain branching in the polyethenes, as measured by dynamic rheometry, depended heavily on the catalyst and polymerization conditions. In a semibatch flow reactor, the level of branching in the polyethenes produced with Et[Ind]₂ZrCl₂/MAO increased as the ethene concentration decreased or the polymerization time increased. The introduction of hydrogen or comonomer suppressed branching. Under similar polymerization conditions, the two other catalyst systems, (n‐BuCp)₂ZrCl₂/MAO and Et[IndH₄]₂ZrCl₂/MAO, produced linear or only slightly branched polyethene. On the basis of an end‐group analysis by FTIR and molecular weight analysis by GPC, we concluded that a chain transfer to ethene was the prevailing termination mechanism with Et[Ind]₂ZrCl₂/MAO at 80 °C in toluene. For the other catalyst systems, β‐H elimination dominated at low ethene concentrations. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 376–388, 2000     

Isospecific copolymerization of styrene and a styrene‐terminated polyisoprene macromonomer with the Ni(acac)2/MAO catalyst

The copolymerization of styrene (St) with a styrene‐terminated polyisoprene macromonomer (SIPM) by a nickel(II) acetylacetonate [Ni(acac)₂] catalyst in combination with methylaluminoxane (MAO) was investigated. A SIPM with a high terminal degree of functionalization and a narrow molecular weight distribution was used for the copolymerization of St. The copolymerization proceeded easily to give a high molecular weight graft copolymer. After fractionation of the resulting copolymer with methyl ethyl ketone, the insoluble part had highly isotactic polystyrene in the main chain and polyisoprene in the side chain. Lowering the MAO/Ni molar ratio and the polymerization temperature were favorable to producing isospecific active sites. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1241–1246, 2000     

Poly(aryl ether)s containing o‐terphenyl subunits. III. Random copoly(ether imide)s

The synthesis of a new diamine monomer, N‐n‐butyl 3,12‐diamino‐5,6,9,10‐tetrahydro[5]helicene‐7,8‐dicarboxylic imide (4), that contains a helically locked, U‐shaped 4′,4″‐o‐terphenyl moiety is described. The monomer was polymerized with 3,3′,4,4′‐oxydiphthalic dianhydride and 2,2‐bis[4‐(4‐aminophenoxy)phenyl]propane to form a series of copoly(ether imide)s (5a–e). The incorporation of 4 into the poly(ether imide)s varied the glass‐transition temperature of the copolymers of which it was a part. There was a tendency to form macrocyclic materials at higher molar percentages of 4 during polymerization. The fluorescence of all the copoly(ether imide)s gradually decreased as the content derived from monomer 4 increased in the polymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 758–763, 2000     

Synthesis of poly(naphthalenecarboxamide)s with low polydispersity by chain‐growth condensation polymerization

Condensation polymerization of 6‐(N‐substituted‐amino)‐2‐naphthoic acid esters ( 1 ) was investigated as an extension of chain‐growth condensation polymerization (CGCP). Methyl 6‐(3,7‐dimethyloctylamino)‐2‐naphthoate ( 1b ) was polymerized at ?10 °C in the presence of phenyl 4‐methylbenzoate ( 2 ) as an initiator and lithium 1,1,1,3,3,3‐hexamethyldisilazide (LiHMDS) as a base. When the feed ratio [ 1a ]₀/[ 2 ]₀ was 10 or 20, poly(naphthalenecarboxamide) with defined molecular weight and low polydispersity was obtained, together with a small amount of cyclic trimer. However, polymer was precipitated during polymerization under similar conditions in [ 1a ]₀/[ 2 ]₀ = 34. To increase the solubility of the polymer, monomers 1c and 1d with a tri(ethylene glycol) (TEG) monomethyl ether side chain instead of the 3,7‐dimethyloctyl side chain were synthesized. Polymerization of the methyl ester monomer 1c did not proceed well, affording only oligomer and unreacted 1c , whereas polymerization of the phenyl ester monomer 1d afforded well‐defined poly(naphthalenecarboxamide) together with small amounts of cyclic oligomers in [ 1d ]₀/[ 2 ]₀ = 10 and 29. The polymerization at high feed ratio ([ 1d ]₀/[ 2 ]₀ = 32.6) was accompanied with self‐condensation to give polyamide with a lower molecular weight than the calculated value. Such undesirable self‐condensation would result from insufficient deactivation of the electrophilic ester moiety by the electron‐donating resonance effect of the amide anion. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Living anionic polymerization of ethylphenylketene: A novel approach to well‐defined polyester synthesis

A living polymerization of ethylphenylketene (EPK) was accomplished. When polymerization of EPK was carried out with butyllithium as an initiator in tetrahydrofuran (THF) at −20 °C, EPK was completely consumed within 5 min, and the corresponding polyester with narrow molecular weight distribution (M_w /M_n ∼ 1.1) was obtained almost quantitatively. Kinetic study of the polymerization at −78 °C revealed that conversion of EPK agreed with the first‐order kinetic equation, and that M_n of the polymer increased in virtually direct proportion to the conversion. Along with these results, successful results in postpolymerization at −20 °C strongly supported living mechanism of the present polymerization. Further, lithium alkoxides having a methoxy group, styryl moiety, and nitroxyl radical, also successfully initiated polymerization of EPK to afford the corresponding polymers having functional initiating ends. In the polymerization with varying feed ratio [EPK]₀/[initiator]₀, the linear relationship between the feed ratio and M_n of the obtained polymer was observed, while maintaining narrow M_w /M_n. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1073–1082, 2000     

Polymerization of methyl methacrylate by metallocene imido complexes and tris(pentafluorophenyl)alane

The polymerization of methyl methacrylate (MMA) was investigated with tris(pentafluorophenyl)alane [Al(C₆F₅)₃] and four metallocene imido complexes that varied in the complex symmetry/chirality, metal, and R group in the ?NR moiety, as well as a zirconocene enolate preformed from the imido zirconocene and MMA. This study examined four aspects of MMA polymerization: the effects of the metallocene imido complex structure on the polymerization activity and polymer tacticity, the degree of polymerization control, the elementary reactions of the imido complex with Al(C₆F₅)₃ and MMA, and the polymerization kinetics and mechanism. There was no effect of the imido complex symmetry/chirality on the polymerization stereochemistry; the polymerization followed Bernoullian statistics, producing syndiotactic poly(methyl methacrylate)s with moderate (～70% [rr]) to high (～91% [rr]) syndiotacticity, depending on the polymerization temperature. Polymerization control was demonstrated by the number‐average molecular weight, which increased linearly with an increase in the monomer conversion to 100%, and the relatively small and insensitive polydispersity indices (from 1.21 to 1.17) to conversion. The reactions of the zirconocene imido complex with Al(C₆F₅)₃ and MMA produced the parent base‐free imido complex and the [2 + 4] cycloaddition product (i.e., zirconocene enolate), respectively; the latter product reacted with Al(C₆F₅)₃ to generate the active zirconocenium enolaluminate. The MMA polymerization with the metallocene imido complex and the alane proceeded via intermolecular Michael addition of the enolaluminate to the alane‐activated MMA involved in the propagation step. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3132–3142, 2003