Lon J. Mathias

Binary frontal polymerization: A new method to produce simultaneous interpenetrating polymer networks (SINs)

We report a new method for the preparation of a simultaneous interpenetrating polymer network (SIN) using a thermal propagating front of two independent and noninterfering polymerization mechanisms. The system consists of the free radical crosslinking of triethylene glycol dimethacrylate (TGDMA) and the amine/BCl3 · amine curing of diglycidyl ether of bisphenol A (DGEBA). The front velocity dependence on the percentage of each monomer shows a minimum at 45% TGDMA. Temperature profile measurements indicate that a single reaction front propagates. A colored opaque material is produced, but SEM and TEM analysis were inconclusive whether phase separation occurred. Samples as large as 5 cm in diameter were prepared with this method. We conclude that this method should be especially suited for preparing large samples of IPNs in which significant phase separation occurs.

Inverse phase transfer catalysis. First report of a new class of interfacial reactions

Transport de nucleophiles (aminopyridines) soluble en phase organique, dans la phase aqueuse reactive)

Synthesis, characterization, and antibacterial activities of novel methacrylate polymers containing norfloxacin.

A novel methacrylate monomer containing a quinolone moiety was synthesized and homopolymerized in N,N-dimethylformamide (DMF) by using azobisisobutyronitrile (AIBN) as an initiator. The new monomer was copolymerized with poly(ethylene glycol) methyl ether methacrylate (MPEGMA) in DMF using the same initiator. The monomer, homopolymer, and copolymer were characterized by elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), size exclusion chromatography (SEC), FTIR, (13)C NMR, and (1)H NMR. The antibacterial activities of the monomer as well as polymers were investigated against Staphylococcus aureus and Escherichia coli, which are representative of Gram-positive and Gram-negative bacteria, respectively. All compounds showed excellent antibacterial activities against these two types of bacteria. The antibacterial activities were determined using the shaking flask method, where 25 mg/mL concentrations of each compound were tested against 10(5) CFU/mL bacteria solutions. The number of viable bacteria was calculated by using the spread plate method, where 100 microL of the incubated antibacterial agent in bacteria solutions were spread on agar plates and the number of viable bacteria was counted after 24 h of incubation period at 37 degrees C.

Synthesis and photopolymerization kinetics of new flexible diacrylate and dimethacrylate crosslinkers based on C18 diacid

Abstract A series of new di(meth)acrylate monomers was synthesized from the reactions of methyl α-hydroxymethylacrylate (MHMA), ethyl α-hydroxymethylacrylate (EHMA), hydroxyethyl acrylate (HEA) and hydroxyethylmethacrylate (HEMA) with α,ω-C18 diacid chloride. The photopolymerization behavior and reaction kinetics of the synthesized monomers were investigated using photoinitiation with differential scanning calorimetry. The polymerization rates, conversions and kinetic constants for propagation and termination were determined for each of the monomers. The maximum rate of polymerizations of the diacrylate monomers was higher than that of the dimethacrylate monomers and followed the order: HDDA (1,6-hexanediol diacrylate)>HEA-C18>EHMA-C18∼HEMA-C18>MHMA-C18. The total conversions obtained were 78, 75, 72, 64 and 69% for MHMA-C18, EHMA-C18, HEMA-C18, HEA-C18 and HDDA, respectively, indicating comparable or higher conversions for methacrylates despite their lower rates of polymerization. Propagation and termination mechanisms of the monomers were investigated by plotting propagation and termination rate constants as a function of conversion.

Highly soluble polyimides from sterically hindered diamines

Polyimides with enhanced solubility have been synthesized from various aromatic tetracarboxylic dianhydrides and sterically hindered diamines. Intrinsic viscosities in 1-methyl-2-pyrrolidinone (NMP) ranged from 0.28 to 1.05 dL/g. Most of the polyimides were soluble in common solvents such as N,N-dimethylacetamide, NMP, chloroform and tetrahydrofuran. Polyimides derived from thianthrene-2,3,7,8-tetracarboxylic dianhydride (TDAN) and diamino mesitylene (DAM) or diethyltoluene diamine (DETDA) were insoluble in all solvents indicating that polyimide solubility decreased as anhydride rigidity increased. Glass transition temperatures ranged from 252 to 398°C and above with the polymers showing little or no weight loss by TGA up to 400°C in both air and nitrogen. The glass transition temperatures of the polyimides increased 15 to 98°C (compared to unhindered polyimide analogs) when one or more methyl group was placed ortho to the imide nitrogen, hindering backbone rotation, chain packing and flexibility. Tough, transparent films of the soluble polyimides were cast from solution.

Cyclopolymerization of ether dimers of α-(hydroxymethyl)acrylic acid and its alkyl esters: substituent effect on cyclization efficiency and microstructures

Abstract Free-radical cyclopolymerization of six ether dimers of α-(hydroxymethyl)acrylic acid and its alkyl esters was kinetically investigated to evaluate the factors that control the cyclopolymerizability. A strong effect of ester substituent on cyclopolymerizability was observed and cyclization efficiency at 80°C increased in the following order: methyl, ethyl, isobornyl, t-butyl and adamantyl esters. That is, cyclization efficiency is found to be affected by the number of carbons linked to the central ester carbon (which defines the ‘effective’ bulkiness) rather than by the ‘apparent’ bulkiness, which encompasses the total mass or size of the whole substituent. Kinetic considerations of the temperature dependence of cyclization efficiency indicated that a strong contribution of the steric factor for bulky substituents (which inhibits intermolecular monomer addition) resulted in high cyclization efficiency despite a disadvantage in activation energy for cyclization. A linear relationship between the difference of activation energies ( E c − E i ) and the logarithm of the ratio of collision frequency factors ( ln ( A c A i ) ) observed for various esters led to recognition of an iso-efficiency point at which all esters show the same cyclization efficiency ( k c k i = 2.0 mol l −1 at −45°C). This phenomenon is caused by the fact that both parameters change in proportion to the bulkiness of the ester substituent. The ether dimer of α-(hydroxymethyl)acrylic acid showed unexpectedly high cyclization efficiency (intermediate between secondary and tertiary esters) despite having the lowest substituent bulkiness. The kinetic parameters obtained showed some deviation from the linearity observed for the ester derivatives. The large A c A i obtained was attributed to the capability of hydrogen-bond formation between acid groups, which causes a favourable conformation for cyclization. Microstructures of the cyclopolymers were investigated by observation of carbonyl carbon peaks in the 13 C nuclear magnetic resonance spectra. The peaks observed were assigned to four microstructures based on the combination of trans/cis configuration of the tetrahydropyran ring and racemic/meso configuration between the rings. Both the trans and racemic ratios increased with the bulkiness of the ester substituent. The values of E cis − E trans and A trans A cis for the t-butyl ester cyclopolymer indicated that trans formation is slightly favourable in both activation energy and steric factor, a result similar to that reported for the racemic/meso ratio in radical polymerization of some alkyl methacrylates. On the other hand, racemic formation between rings was suggested to be sterically unfavourable by the A racemic A meso ratio = 0.55 . The glass transition temperatures for the cyclopolymers were found to be much higher than for the corresponding acrylates or methacrylates, and the thermal stabilities of some of the derivatives, especially the adamantyl compound, were also high.

Hyperbranched poly(3-ethyl-3-hydroxymethyloxetane) via anionic polymerization

Abstract Anionic polymerization of 3-ethyl-3-hydroxymethyl oxetane was achieved using NaH with coinitiators benzyl alcohol (BA) or trimethylol propane (TMP). Pendent hydroxyls facilitate a multibranching polymerization. NMR confirmed the presence of linear, dendritic, and terminal repeat units. For TMP initiated polymerizations there was an acetone soluble portion which was more branched (DB=0.48) than the acetone insoluble portion (DB=0.20). Polymers were not soluble in water, ether or THF, but were partially soluble in acetone and completely soluble in methanol, benzene, chloroform, and DMSO. MALDI-TOF analysis showed relatively low molecular weights (around 500) and confirmed the presence of both cyclic and TMP endgroups.

Synthesis of 3-alkylated-1-vinyl-2-pyrrolidones and Preliminary Kinetic Studies of their Photopolymerizations

Abstract 1,6-Bis-3-(vinyl-3-2-pyrrolidonyl)hexane (BNVP) was synthesized for use as a crosslinker in the photopolymerization of 1-vinyl-2-pyrrolidone (NVP). A model compound, 3-hexyl-1-vinyl-2-pyrrolidone (HNVP), was also synthesized for use as a model comonomer in the kinetic studies of NVP copolymerization. Copolymerizations with NVP and low feed ratios of HNVP indicate that alkyl substitution in the 3-position on the pyrrolidone ring does not affect radical reactivity of the monomer. However, the comonomer containing this hexyl side chain acted as an internal plasticizer for the NVP polymers, lowering the T g and reducing the effect of autoacceleration on the photopolymerization process. The crosslinked polymers exhibited gel-like swelling in water. The crosslinker limited the mobility of the polymer chains early in the polymerization and induced earlier onset of the Tromsdorff effect.

Synthesis and Characterization of Novel Aromatic Polyimides from 4,4-Bis(p-Aminophenoxymethyl)-1-Cyclohexene

A novel diamine, 4,4-bis(p-aminophenoxymethyl)-1-cyclohexene (CHEDA), was synthesized from 4,4-bis(hydroxymethyl)-1-cyclohexene and p-chloronitrobenzene by nucleophilic aromatic substitution and subsequent catalytic reduction of the intermediate dinitro compound. A series of aromatic polyimides were prepared from CHEDA and commercial dianhydrides with varying flexibility and electronic character in two-step direct polycondensation reactions. High molecular weight polyimides with intrinsic viscosities between 0.57 and 10.2 dL/g were obtained. Most of these polyimides, excluding those from PMDA and BPDA, were soluble in polar aprotic solvents such as NMP and DMAc, and many were also soluble in CHCl3 and THF. DSC analysis revealed glass transitions in the range of 190 to 250°C. No significant weight losses occurred below 450°C in nitrogen and 350°C in air. Bromination and epoxidation of cyclohexene double bond in CHDEA–6FDA (3e) were investigated as examples of possible polymer modifications. Qualitative epoxidation and selective bromination of the double bond were demonstated.

Synthesis and Cyclopolymerization of Novel Allyl-Acrylate Quaternary Ammonium Salts

Novel allyl-acrylate quaternary ammonium salts were synthesized using two different methods. In the first (method 1), N,N-dimethyl-N-2-(ethoxycarbonyl)allyl allylammonium bromide and N,N-dimethyl-N-2-(tert-butoxycarbonyl)allyl allylammonium bromide were formed by reacting tertiary amines with allyl bromide. The second (method 2) involved reacting N,N-dialkyl-N-allylamine with either ethyl α-chloromethyl acrylate (ECMA) or tert-butyl α-bromomethyl acrylate (TBBMA). The monomers obtained with the method 2 were N,N-diethyl-N-2-(ethoxycarbonyl)allyl allylammonium chloride, N,N-diethyl-N-2-(tert-butoxycarbonyl)allyl allylammonium bromide, and N,N-piperidyl-N-2-(ethoxycarbonyl)allyl allylammonium chloride. Higher purity monomers were obtained with the method 2. Solution polymerizations with 2,2′-azobis(2-amidinopropane) dihydrochloride (V-50) in water at 60–70°C gave soluble cyclopolymers which showed polyelectrolyte behavior in pure water. Intrinsic viscosities measured in 0.09M NaCl ranged from 0.45 to 2.45 dL/g. 1H- and 13C-NMR spectra indicated high cyclization efficiencies. The ester groups of the tert-butyl polymer were hydrolyzed completely in acid to give a polymer with zwitterionic character.