Abstract: The porosity and flow characteristics of macroporous polymer monoliths that may be used to prepare separation media, flow-through reactors, catalysts, or supports for solid-phase chemistry can be controlled easily during their preparation. Key variables such as temperature, composition of the pore-forming solvent mixture, and content of cross-linking divinyl monomer allow the tuning of average pore size within a broad range spanning 2 orders of magnitude. The polymerization temperature, through its effects on the kinetics of polymerization, is a particularly effective means of control, allowing the preparation of macroporous polymers with different pore size distributions from a single composition of the polymerization mixture. The choice of pore-forming solvent is also important, larger pores being obtained in a poor solvent due to an earlier onset of phase separation. Increasing the proportion of the cross-linking agent present in the monomer mixture not only affects the composition of the final monolit...

Abstract: The catalyst system based on lanthanide tris(2,6-di-tert-butylphenolate)s ands various alcohols was found to be very effective in the solution polymerization of L-lactide, e-caprolactone and δ-valerolactone. Good control over molecular weight, molecular weight distribution and end groups can be exerted

Abstract: A new method for the synthesis of poly(dichlorophosphazene) at ambient temperatures is described It involves the initiation of Cl3PNSiMe3 with small amounts of PCl5 in CH2Cl2 to yield poly(dichlorophosphazene), (NPCl2)n, with narrow polydispersities The molecular weight of poly(dichlorophosphazene) was controlled by altering the ratio of monomer to initiator The polymer chains were found to be active after chain propagation since further addition of monomer resulted in the formation of higher molecular weight polymer Integration of 1H and 31P NMR spectra of these reactions revealed that the polymerization follows first-order reaction kinetics with respect to monomer concentration Active polymer chains may be quenched or end-capped by the addition of trace quantities of Me2(CF3CH2O)PNSiMe3 or (CF3CH2O)3PNSiMe3 Furthermore, PBr5, SbCl5, and Ph3C[PF6] were also found to be effective initiators in CH2Cl2 at room temperature

Abstract: Polymerization of l-lactide in dichloromethane at 25 °C using an initiating system comprising tris(2,6-di-tert-butylphenoxy)yttrium and 2-propanol was first order in monomer and initiator. A propagation rate constant of 1.92 × 103 L mol-1 min-1 was determined using in situ UV spectroscopy. In the first step the large 2,6-di-tert-butylphenoxy ligands are exchanged for the sterically less demanding 2-propoxide ligands. In the second step the alkoxide is able to attack the carbonyl group with formation of the ring-opened product. After the first two initiating steps the polymerization can proceed until the equilibrium conversion of monomer is reached. Evidence for these three steps is provided by 1H and 13C NMR spectroscopy of the reaction products of each step. The kinetic behavior of commercially available yttrium isopropoxide was more complicated.

Abstract: It is shown that the oxidative solution polymerization of 2-tetradecylthieno[3,4-b]-1,4-dioxin results in soluble polymers with optical and redox properties similar to those of electrochemically prapared insoluble films

Abstract: End-functional aliphatic polyesters have been synthesized by ring-opening polymerization (ROP) of e-caprolactone (e-CL) and lactides (LA). Polymerization initiated with any of the functional aluminum alkoxides of the general structure Et3-pAl(OCH2X)p, where p = 1 and 3, obeys a living “coordination−insertion” mechanism, under suitable conditions (temperature, concentration, and solvent), with the formation of α-functional chains of a predictable molecular weight. A kinetic study has emphasized the importance of the cyclic monomer (e-CL or LA) and the key role of the initiator structure: the number of functional alkoxides per aluminum and the nature of the functional group (X = CH2Br, (CH2)2CHCH2, (CH2)2NEt2). Activation enthalpy and entropy have been calculated for the e-CL polymerization initiated by several aluminum alkoxides at various temperatures. The effects of solvent (toluene or tetrahydrofuran) and purification of the aluminum monoalkoxides by distillation under reduced pressure have also been c...

Abstract: The results are reported for a series of measurements of the propagation rate coefficient (kp) of butyl acrylate obtained from pulsed-laser polymerization (PLP). Previous attempts reported in the l...

Abstract: The steric effect of bulky groups of the catalyst can kinetically suppress the transesterification reactions by screening linear polymer chains from the active center during the polymerization of e...

Abstract: Studies were undertaken to gain mechanistic information on lactone ring-opening polymerization reactions using porcine pancreatic lipase (PPL) as the catalyst and e-caprolactone (e-CL) as the monomer. Polymerizations were carried out at low water levels (0.13 mmol) and supplemented with either butanol or butylamine. Rates of monomer conversion, product molecular weight, total chain number, and chain end structure were determined by 1H NMR. In the presence of water alone, a maximum Mn of 7600 g/mol was obtained at 85% conversion, which decreased to 4200 g/mol as the reaction continued to 98% conversion. Reactions with butanol and butylamine at 100% conversion gave polymers with Mn values of 1900 and 1200 g/mol, respectively. For these three polymerizations, the total number of polymer chains increased with conversion due to a simultaneous increase in carboxylic acid chain ends. Within 4 h (∼26% monomer conversion), butylamine was completely consumed but only 37% of butanol reacted. Reactions with butylamin...

Abstract: e-Caprolactone polymerization using an initiating system comprising tris(2,6-di-tert-butylphenoxy)yttrium and 2-propanol was first-order in monomer and initiator. A propagation rate constant of 1.65 L·mol-1·s-1 was determined in dichloromethane. The reaction proceeds via a three-step mechanism. In the first step the large 2,6-di-tert-butylphenoxy ligands are exchanged for the smaller 2-propanol. In the second step the polar alkoxide is able to attack the carbonyl group and form the thermodynamically favored ring-opened product. After the first two initiating steps, the polymerization can proceed until complete conversion of monomer is reached. Evidence for these three steps is provided by 1H and 13C NMR spectroscopy of the reaction products of each single step. The kinetic behavior of commercially available yttrium isopropoxide was more complicated. 2-Propanol could be used as an effective chain transfer agent for this initiator.

Abstract: Enzymatic oxidative polymerization of 2,6-dimethylphenol has been carried out in an aqueous organic solvent at room temperature under air. Laccase derived from Pycnoporus coccineous and horseradish...

Abstract: The lipase-catalyzed stereoelective ring-opening polymerization of racemic α-methyl-β-propiolactone (MPL) was investigated. Using the lipase PS-30 from Pseudomonas fluorescens, a direct route to optically active (S)-enriched poly(α-methyl-β-propiolactone), PMPL, was demonstrated. From a comparative study of different organic media, polymerizations conducted in toluene and heptane proceeded more rapidly than those carried out in dioxane. The enantiomeric ratios E in toluene, heptane, and dioxane were 4.1 ± 0.2, 0.9, and 2.0, respectively. Thus, from the point of view of reaction rates and enantioselectivity, toluene was found to be the preferred solvent. PMPL products prepared in toluene by PS-30 catalysis had Mn values from 2600 to 2900 g/mol and [α]25D +12.2° to +19.0° (c 0.9 g/dL, CHCl3). Analysis of the polymer chain end structure by 1H and 13C NMR showed that these products have hydroxyl and carboxylic acid termini. Based on the analysis of chain stereosequence distributions by 13C NMR, it was conclud...

Abstract: Solution copolymerization of acrylonitrile (AN) with various vinyl acids, i.e., acrylic acid (AA), methacrylic acid (MAA), and itaconic acid (IA), was carried out in DMF at 70°C using α,α′-azobisisobutyronitrile (AIBN) as an initiator with an acidic monomer of 0.012–0.092 mol %. Copolymers were characterized by FTIR, CHN analysis, 1H-and 13C-NMR, and viscometry. The reactivity ratios were calculated using Fineman–Ross and Kelen–Tudos methods. In all three systems, the value of r1 (AN) is much less than the value of r2. However, the r2 (MAA) is higher than r2 of (AA) and (IA). The reactivity ratios were calculated using Q and e schemes also. The results are in good agreement with experimentally calcualted data. The tacticity and sequence length distribution of these copolymers were calculated using 13C-NMR from CN and CH signals. It was observed that the isotacticity of acrylonitrile–itaconic acid copolymer P(AN–IA) with 8.2 mol % of a comonomer is lower than that of P(AN–MAA) with 10.3 mol % and P(AN–AA) with 7.61 mol %. © 1996 John Wiley & Sons, Inc.

Abstract: A number of mixed aromatic/cycloaliphatic as well as fully nonaromatic polyimides have been prepared. Whereas all the poly(amic acids) derived from nonaromatic diamines involved salt-formation during the initial stages of the polymerization, the majority of these eventually formed homogeneous, highly viscous polymer solutions. Only in a few select cases involving all nonaromatic monomers traditional solution polymerization was unsuccessful. The polyimide derived from hexafluoroisopropylidene diphthalic anhydride (6FDA) and trans- 1,4-diaminocyclohexane (DACH) yielded films with tough mechanical properties, a glass transition temperature of ∼360°C, good solvent resistance, and a low dielectric constant of 2.6. Thermal stability of this polyimide as determined by thermal gravimetric analysis in both air and nitrogen was quite good, exhibiting a weight loss of only 0.07 wt%/h at 350°C under isothermal conditions in nitrogen. However, mechanical properties as a function of thermal aging in both air and nitrogen indicated a maximum use temperature of only 350°C under inert conditions and less than 300°C in the presence of oxygen.

Abstract: High-impact-modified polystyrene (HIPS) is made by thermal or radical polymerization of styrene containing dissolved polybutadiene (PB). The reaction leads, intermediately, to blends of yet ungrafted PB, of the homopolymer PS, and of graft copolymers PBgS varying in the number of PS grafts per PB chain. The polymerization induces a phase separation and a phase inversion which results in the well-known “salami” morphology of HIPS. To elucidate the mechanism producing this morphology, the polymerization of styrene in PB/styrene mixtures was studied kinetically and morphologically, in toluene solution and in the bulk. Besides the conventional techniques of polymerization kinetics, electron microscopy was employed to examine the PS/PB/PBgS blends that are formed during the polymerization. The electron micrographs reflect sensitively the composition of these blends, the architecture of the PBgS graft copolymers, and the miscibility of PBgS with PS and PB. The blends were isolated from the polymerizing system b...

Abstract: An automated reaction calorimeter was used to directly monitor the rate of emulsion polymerization of styrene using different emulsifier (sodium lauryl sulfate) and initiator (potassium persulfate) concentrations. By using this technique in conjunction with off-line measurements of the evolution of the particle size distributions, important details of the process were observed. The classical constant rate period (Interval II) often reported for the batch emulsion polymerization of styrene was not seen in this work. Instead, the experimental results suggest that the end of nucleation and the disappearance of monomer droplets take place at approximately the same conversion (36-40%). From the polymerization rate data, important parameters such as the monomer concentration in the polymer particles and the average number of radicals per particle were calculated.

Abstract: Ring-opening polymerization of e-caprolactone catalyzed by rare earth halides and rare earth halide−epoxide has been carried out for the first time. It was found that rare earth halides have low activities for the polymerization of e-caprolactone, but in the presence of epoxide, rare earth halides are highly active for the bulk and solution polymerization of e-caprolactone, with high molecular weight poly(e-caprolactone) (PCL) formed. With the NdCl3−20PO system, PCL with a molecular weight of 22.4 × 104 can be easily obtained at 30 °C, and the molecular weight of PCL can be increased to 42 × 104 at 60 °C with a catalyst efficiency of 100 × 104 g of PCL/mol of NdCl3. The catalytic activities of the rare earth halides are affected by the kind of rare earth element, halogen, epoxide, amount of added epoxide, catalyst concentration, and polymerization temperature. It has been found that rare earth halides react with epoxide and produce halogen rare earth alkoxides: (X3-xLn{[OCH(R)CH2]yX}x, X = Cl, Br, I). A ...

Abstract: Water-soluble poly(N,N-dimethylacrylamide) (PDMA) and poly(N-acryloyl-N ‘-methylpiperazine (PAMP) were prepared in tetrahydrofuran at −78 °C by anionic polymerization in the presence of monofunctional initiators such as (triphenylmethyl)lithium, or -cesium or the difunctional initiators (1,1,4,4-tetraphenylbutyl)lithium, -potassium, or -cesium or cesium naphthalenide. Polymerizations initiated especially in the presence of cesium as counterion proceeded in a homogeneous manner and gave polymers having controlled molecular weights and narrow molecular weight distributions in quantitative yields. However, the polymerization results in polymers with a lower molecular weight and a broad molecular weight distribution at higher reaction temperatures. Size exclusion chromatography, 1H NMR spectroscopy, and intrinsic viscosity measurements support the clean anionic polymerization of DMA with few side reactions at −78 °C. Attempted anionic polymerizations of methacrylamide monomers such as N,N-dimethylmethacrylami...

Abstract: A process for homo or copolymerizing propylene, wherein propylene is polymerized in the presence of a catalyst at an elevated temperature in a reaction medium in which a major part of the reaction medium is propylene and the polymerization is carried in at least one CSTR or loop reactor, where the polymerization is carried out at a temperature and a pressure which are above the corresponding critical temperature and the pressure of the reaction medium and where the residence time is at least 15 minutes. The process can also comprise a subcritical loop polymerization before the supercritical stage polymerization or a gas phase polymerization after the supercritical stage polymerization.

Abstract: Pronounced Effects of Temperature and Monomer Concentration on Isotactic Specificity of Triphenylmethyl Methacrylate Polymerization through Free Radical Mechanism. Thermodynamic versus Kinetic Control of Propagation Stereochemistry

Abstract: This invention is a solution process for the preparation of high molecular weight ethylene-α-olefin-diolefin copolymers comprising contacting ethylene, one or more α-olefin monomers, and optionally one or more diene monomers, with a catalyst system at a polymerization temperature at or above about 80 °C, ethylene, one or more α-olefin monomers, and optionally one or more diene monomers, with a catalyst system comprising an unbridged Group 4 metal compound having a bulky monocyclopentadienyl ligand, a uninegative bulky Group 15 ligand and two uninegative, activation reactive ligands and a catalyst activator compound. The process can be advantageously practiced at a reaction temperature of at least 80 °C, most preferably above 100 °C, to achieve high number average molecular weight polymer having high α-olefin monomer and diene monomer contents with high diene conversion rates. The process is particularly suitable for the preparation of elastomeric ethylene-propylene or ethylene-propylene-diene monomer elastomers.

Abstract: The present invention is directed to a novel supported Ziegler-Natta catalyst useful for the polymerization of α-olefins. More specifically, the supported Ziegler-Natta catalyst of the present invention comprises a particulate functionalized copolymeric support, an organometallic compound and a transition metal compound. A novel method of preparing the particulate functionalized copolymeric supports of the instant invention is also provided.

Abstract: For many applications such as enhanced oil recovery, it is essential to have an extremely water soluble shear stable polymer that can impart high viscosity at very low concentration for economic reasons. It is known that rigid rod polymers can deliver high viscosity at low molecular weight compared with the traditionally used flexible chain polymers such a hydrolyzed polyacrylamides. Polymers with helical or double stranded conformations may be considered as truly rigid rod in solution. New sulfonated water soluble aromatic polyamides, polyureas, and polyimides were prepared via interfacial or solution polymerization of sulfonated aromatic diamines with aromatic dianhydrides, diacid chlorides, or phosgene. Some of these polymers had sufficiently high molecular weight (<200,000), extremely high intrinsic viscosity (∼ 65 dL/g), and appeared to transform into a helical coil in salt solution. These polymers have been evaluated in applications such as thickening of aqueous solutions, flocculation and dispersion stabilization of particulate materials, and membrane separation utilizing cast films. © 1996 John Wiley & Sons, Inc.

Abstract: The polymerization of 2-acetoxymethyl-2-alkyltrimethylene carbonates (alkyl = methyl : AMTC, alkyl = ethyl : AETC) and of 2-methoxycarbonyl-2-methyltrimethylene carbonate (MMTC) in toluene with see-butyllithium as initiator results in the respective polymer with yields between 78% and 88%. The analysis of the polymer microstructure by means of NMR spectroscopy reveals linear chains without branching due to an attack of the active chain end at the ester moiety of the repeating units. Poly(MMTC) and poly(-AETC) afford crystalline materials upon precipitation from solution while poly- (AMTC) is amorphous ; after quenching from the melt all materials are amorphous. Copolymerization of AMTC, AETC and MMTC with 2,2-dimethyltrimethylene carbonate (DTC) results in random copolymers. The kinetics of the polymerization of AETC and MMTC revealed that the ester side chain enhances the rate of propagation compared to the polymerization of DTC. The apparent rate constants of propagation in toluene with lithium alcoholate as active sites at 23°C were determined to be k app DTC = 4. 10 -3 s -1 , k app AETC = 4,28. 10 -2 s -1 , and k app MMTC = 2,57. 10 -2 s -1 . Studies of ring-chain equilibria in solution of tetrahydrofuran revealed that on the basis of the theory of Jacobson-Stockmayer the characteristic ratios of the polymers are C∞ PDTC = 7,1, C∞ PMMTC = 8,6, C∞ PAETC = 9,9, and C∞ PAMTC = 13,4.

Abstract: A process for producing a substantially dry polymer particle powder. A mixture of polymerization reagents is formed from a mixture of at least one monomer source and a solvent selected from the group consisting essentially of water and organic solvents and an initiator source. The mixture of polymerization reagents is sprayed into a heated, controlled atmosphere, forming droplets of the mixture which are allowed to fall through the heated, controlled atmosphere for a sufficient period of time to obtain a desired degree of polymerization. The solvent is continuously evacuated from the atmosphere during the polymerization process.

Abstract: Low molecular weight, highly reactive polyisobutene having an average molecular weight Mn of from 500 to 20000 Dalton and containing over 80 mol % of terminal double bonds is prepared by the polymerization of isobutene or an isobutene-containing hydrocarbon stream in the liquid phase and with the aid of a boron trifluoride complex catalyst at from -40 to 0° C. and at from 1 to 20 bar, by a process in which the polymerization reaction is carried out in at least two polymerization stages, the added isobutene being polymerized to a partial conversion of up to 95% in the first polymerization stage and the polymerization of the remaining isobutene being continued in one or more subsequent polymerization stages, without or after prior isolation of the polyisobutene formed in the first polymerization stage.