The molecular structures of (RS)-1,2-diphenylethyl methacrylate and (RS)-α-tert-butylbenzyl methacrylate

The molecular structures of (RS)-1,2-diphenylethyl methacrylate (DPEMA) and (RS)-α-tert-butylbenzyl methacrylate (t-BBMA) were determined by means of X-ray diffraction. Crystals of (RS)-DPEMA are monoclinic, space group C2/c, a = 33,341(3), b = 5,916(1), c = 15,911(2) Å, β = 106,42(1)°, and Z = 8. Crystals of (RS)-t-BBMA are also monoclinic, space group P2₁/c, a = 6,028(1), b = 31,009(3), c = 15,207(1) Å, β = 96,780(8)°, and Z = 8. Both structures were solved by the direct method and refined by the block-diagonal least-squares procedure: DPEMA, R = 0,113 for 1 100 observed reflections and t-BBMA, R = 0,081 for 2206 non-zero reflections, respectively. The molecule of DPEMA has an antiperiplanar conformation as to the C?C and C?O double bonds about the C(1)? C(2) bond, a synperiplanar conformation as to the C?O and C? O bond about the C(1)? O(1) bond, and an anticlinal conformation about the O(1)? C(5) bond. One of the two t-BBMA molecules in an asymmetric unit has an antiperiplanar conformation as to the C?C and C?O double bonds about the C(1)? C(2) bond, whereas the other antiperiplanar molecule may contain some synperiplanar conformation. Both molecules have a synperiplanar conformation as to the C?O and C? O bonds about the C(1)? O(1) bond and an anticlinal conformation about the O(1)? C(5).     

Studies on helix-sense-selective copolymerization based on triphenylmethyl methacrylate

Helix-sense-selective copolymerizations based on triphenylmethyl methacrylate (TrMA) with methyl methacrylate (MMA), benzyl methacrylate (BzMA) and diphenylmethyl methacrylate (DPMMA) in the presence of the chiral anionic complex initiator (?)-sparteine/9-fluorenyl-lithium ( 1 ) were investigated. The studies concentrated on the stereoregularity of the copolymers, the relative reactivity of the monomers, the specific rotation of the copolymers and the influence of the solvent on the copolymerization. The results show that the match of TrMA with MMA of smaller size would favour the form of the copolymer with isotactic one-handed helix having higher specific rotation as compared with BzMA ad DPMMA in toluene, but the TrMA/MMA copolymer obtained in tetrahydrofuran possessed a very low specific rotation because of the action of the polar tetrahydrofuran on the anion complex.     

The molecular structure of diphenylmethyl methacrylate

The molecular structure of diphenylmethyl methacrylate has been determined by means of X-ray diffraction. Crystals are monoclinic, space group C2/c, a = 29, 177 (2), b = 6,017(1), c = 16,110(1) Å, β = 96,840(5)°, and Z = 8. The structure was solved by the direct method and refined by the block-diagonal least-squares procedure to R = 0,071 (R_w = 0,091) for 1768 measured reflections. The molecule has an antiperiplanar conformation as to the C?C and C?O double bonds about the C(1)? C(2) bond and a synperiplanar conformation as to the C?O and C? O bonds about C(1)? O(1).     

Axially chiral catalysts for the preparation of optically active poly(triphenylmethyl methacrylate)

A variety of axially dissymmetric diphenylylene diamines 1a — 1f were synthesized and evaluated as chiral auxiliaries for the polymerization of triphenylmethyl methacrylate with organolithium compounds such as butyllithium and lithium (±)-N-(1-phenylethyl)anilide in toluene at ?78°C. The catalysts containing an optically active biphenylylene derivative of tetramethyl-ethylenediamine ( 1e ) were found to be particularly useful for the preparation of optically active poly(triphenylmethyl methacrylate) (PTrMA). The catalysts afforded tetrahydrofuran (THF)-soluble polymers in high yields and the polymers showed large optical rotations arising from a one-handed helical conformation of a polymer chain. (+)- and (-)-PTrMAs were obtained by using (S)- 1e and (R)- 1e , respectively. The poly(methyl methacrylate)s derived from these PTrMAs were almost completely isotactic, but showed negligible optical rotations. The other catalysts produced mainly polymers insoluble in organic solvents; the small amounts of THF-soluble materials showed rather low optical rotations.     

Conformation of phenyl rings in the helical chain polymer poly(triphenylmethyl methacrylate)

The conformation of phenyl rings in the side groups of the helical chain polymer poly(triphenylmethyl methacrylate) ( 1 ) in solution was studied by spectroscopic methods. According to the Raman spectrum the phenyl rings of 1 and triphenylmethyl methacrylate in solution have the same depolarization ratio at 1 002 cm^?1. The electronic spectra (ultraviolet and fluorescence) of 1 are similar to those of model substances, except for the “red shift” of the spectra of about 5 nm. It was concluded that the phenyl rings can rotate around the phenyl? C bond.     

Stability of helical conformation and reactivity of optically active poly(triphenylmethyl methacrylate) in solution

The stability of the helical conformation in optically active poly(triphenylmethyl methacrylate) (PTrMA) was investigated by heating the polymer solutions at 100°C. The optical rotation slowly disappeared with time, and some preliminary experiments showed that this phenomenon is not due to a typical racemization process, as it is accompanied by a loss of triphenylmethyl (Tr) groups due to secondary reaction. Experimental results in the presence of methanol indicated that the decrease of optical activity occurs according to first-order kinetics and qualitatively methyl triphenylmethyl ether was isolated from the final solution. In order to explain the above results, full characterization of copolymers obtained by interrupting the methanolysis at different conversions was performed. As a working hypothesis, it was assumed that the reaction starts at the end of the helices with a Tr-oxygen bond fission and the reaction proceeds along the chain mainly with formation of block copolymers consisting of one block of PTrMA and one block of a probably random methacrylic acid anhydride/methacrylic acid copolymer.     

The molecular structure of 4-(dimethylmaleimido)phenyl methacrylate

The molecular structure of 4-(dimethylmaleimido)phenyl methacrylate was determined by means of X-ray diffraction. Crystals are orthorhombic, space group F2dd, a = 3,993(1) Å, b = 36,650(6) Å, c = 39,460(8) Å and Z = 16; d_calc = 1,360 g · cm^?3, V = 5774,7 ų, M = 285,3, λ = 0,7107 Å, μ (MoK_α) = 1,06 cm^?1, F(000) = 2400. The structure was solved by direct methods and refined to R = 0,062 for 304 observed reflections. The molecule has a synperiplanar conformation as to the C?C and C?O double bonds about C(7)? C(8) and also as to the C?O and C? O bonds about C(7)? O(1).     

Block copolymerization of triphenylmethyl methacrylate with other methacrylates using (−)-sparteine/9-fluorenyllithium as an initiator

Diblock and triblock copolymerization of triphenylmethyl methacrylate (TrMA) with methyl methacrylate (MMA), butyl methacrylate (BuMA), benzyl methacrylate (BzMA) or diphenylmethyl methacrylate (DPMMA) in the presence of the chiral anionic complex initiator, (?)-sparteine/9-fluorenyllithium, were investigated. The resulting block copolymers show high specific rotation and were characterized by means of gel-permeation chromatography, scanning electron microscopy, nuclear magnetic resonance, circular dichroism spectra and thermal analysis.     

The molecular structures of methacrylates with bulky ester substituents, (RS)-1,2,2,2-tetraphenylethyl methacrylate and (1S, 2R)-(+)-1-benzyl-3-dimethylamino-2-methyl-1-phenylpropyl methacrylate

The molecular structures of (RS)-1,2,2,2-tetraphenylethyl methacrylate (TrBzMA) and (1S, 2R)-(+)-1-benzyl-3-dimethylamino-2-methyl-1-phenylpropyl methacrylate (ChMA) were determined by means of X-ray diffraction: (RS)-TrBzMA .0,5C₆H₆; triclinic, space group P1, a = 9,271(2), b = 33,965(4), c = 9,167(2) Å, α = 90,26(2), β = 118,80(2), γ = 88,03(2)°, and Z = 4; ChMA; monoclinic, space group P2₁, a = 12,482(1), b = 9,184(1), c = 9,246(1) Å, β = 93,49(1)°, and Z = 2. Both structures were solved by the direct method and refined by the block-diagonal least-squares procedure to R = 0,054 and 0,057 for non-zero reflections, respectively. Both of the two crystallographically independent molecules of TrBzMA have the same structure; each molecule has a synperiplanar (sp) conformation as to the C?C and C?O double bonds about the C(1)? C(2) bond and also an sp conformation as to the C?O and C? O bonds about the C(1)? O(1) bond. The ChMA molecule has an antiperiplanar (ap) and a sp conformation about the C(1)? C(2) and C(1)? O(1) bonds, respectively.     

Cationic polymerization of anethole by triphenylmethyl hexafluoroantimonate

Cationic polymerizations of anethole in methylene dichloride initiated by triphenylmethyl hexafluoroantimonate were studied by dilatometry and UV-visible spectroscopy at temperatures between 0 and 35°C. Initiator consumption continued throughout polymerization, reaching 85–95%. Monomer conversion ranged from 75 to 98%. Reaction half-lives were on the order of 15 to 60 min at 25°C. Polymer molecular weights were bimodal with some evidence of branching and cross-linking. The principal termination reaction appeared to involve formation of a chromophore absorbing at 501 nm. Rate constants on the order of 10^?3 dm³·mol^?1·s^?1 for initiation and 1 dm³·mol^?1·s^?1 for propagation at 25°C were estimated.     

The influence of molecular interaction on polymerization, 5. Copolymerization of benzyl methacrylate with maleic anhydride

Copolymerization of benzyl methacrylate (BMA) with maleic anhydride (MA), initiated by 2,2′-azoisobutyronitrile at 70°C in chloroform or acetonitrile, were investigated. The complex formation between the two monomers in chloroform was studied by ¹H NMR spectroscopy. The stability constant of the complex was found to be 0,25 l.mol^?1. The following copolymerization reactivity ratios were found: in chloroform: r_BMA = 0,188 ± 0,035 and r_MA = 0,003 ± 0,005, in acetonitrile: r_BMA = 0,116 ± 0,093 and r_MA = 0,231 ± 0,027. By ¹H NMR investigations it could be shown that the results correlate with the changes of the reactivity ratios depending on the solvent used.     

The influence of molecular interaction on polymerization, 9. Copolymerization of 2-naphthyl methacrylate with acrylonitrile

The copolymerization of 2-naphthyl methacrylate (2-NM) with acrylonitrile (AN) initiated by 2,2′-azoisobutyronitrile (AIBN) was carried out in solvents with different dielectric constants. The relative reactivity ratios of the monomers determined by the Fineman-Ross method in the solvents used are as follows:

• in chloroform: r_2-NM = 0,96 ± 0,05; r_AN = 0,00 ± 0,02
• in benzene: r_2-NM = 0,84 ± 0,09; r_AN = 0,01 ± 0,04
• in acetone: r_2-NM = 0,52 ± 0,09; r_AN = 0,00 ± 0,02
• in acetonitrile: r_2-NM = 0,51 ± 0,06; r_AN = 0,00 ± 0,03

The capability of the monomers to form donor-acceptor associates was shown by means of ¹H NMR spectroscopy. The observed interactions between the monomer molecules on one side and between the molecules of the monomers and the solvent on the other side were used to explain the changes in the reactivity ratios of both monomers obtained in different solvents.     

The influence of molecular interaction on polymerization, 8. Copolymerization of monomethyl itaconate with 2-naphthyl methacrylate

The copolymerization of monomethyl itaconate (monomethyl 2-methylenesuccinate, MMI) with 2-naphthyl methacrylate (2-NM) initiated with 2, 2′-azoisobutyronitrile (AIBN) in solvents of different dielectric constants and capability to form hydrogen bonds was investigated. The reactivity ratios of the monomer pairs in the different solvents are as follows: IR and ¹H NMR spectroscopy studies show the influence of the solvent on the capability of the monomers to form hydrogen bonds and donor-acceptor associates. The changes in the reactivity ratios of both monomers are attributed to the interaction observed between the monomer molecules as well as between the molecules of the monomers ad the respective solvent.     

NMR studies of conformation and molecular motion of poly(methyl methacrylate) in solution

NMR shift reagent, tris(dipivalomethanato)europium(III), was applied to the ¹H NMR measurement of isotactic and syndiotactic poly(methyl methacrylate) in solution in the temperature range 25–80°C. The solvents used were benzene (C₆D₆), chloroform (CDCl₃), and carbon tetrachloride (CCl₄). By comparing the observed values of paramagnetically induced shift with the values of geometric factor calculated for several kinds of conformational models hitherto proposed for these polymers, the possible conformations of the respective polymers in solution were eludicated. Furthermore the variation, as a function of temperature, of the carbon-13 spin-lattice relaxation times of individual carbons of isotactic and syndiotactic poly(methyl methacrylate) in benzene and chloroform solutions were measured and the correlation between the molecular motion and the conformation is discussed. It is pointed out that the conformation depends both on the stereochemical configuration and the nature of solvent, and the molecular motion depends both on the conformation and the configuration.     

The unperturbed dimensions of polymethyl methacrylate

The value of K_Θ obtained from [η] method is higher than the value of K_Θ obtained from the measurements in Θ-solvent and over 100% higher than the value of K_Θ obtained from the data using FOX-FLORY-SCHAEFGEN and other equivalent plots. The higher value of K_Θ indicates that the unperturbed dimensions of PMMA are 30% higher in bulk than in dilute solutions perhaps due to influence of the microstructure on the unperturbed dimensions of the polymeric chains.     

Novel water-soluble block copolymers of dimethylaminoethyl methacrylate and dihydroxypropyl methacrylate

In this publication we describe the synthesis and properties of a novel type of block copolymer. The anionically synthesised block copolymer consists of a neutral, watersoluble block (2,3-dihydroxypropyl methacrylate, HMA) and a pH-dependently charged one (2-dimethylaminoethyl methacrylate, AMA). The adsorption on silica and its effect on the colloidal stability were evaluated. The adsorbed amount is mainly determined by the electrostatics, which leads to a maximum adsorbed amount at low AMA content. The block copolymers tend to destabilise colloidal silica, due to a charge neutralisation upon adsorption, which is not compensated by the formation of a steric layer.     

Studies on blood compatibility of terpolymers composed of methyl methacrylate,methoxypolyethyleneglycol methacrylate,and dimethylsiloxane methacrylate

Terpolymers composed of methyl methacrylate (MMA), polydimethylsiloxane methacrylate (PDMSMA), and methoxypolyethyleneglycol methacrylate (MPEGMA), having different compositions were synthesized. Platelets were not adsorbed onto terpolymer surfaces composed of 50 wt% MMA, 25 wt% PDMSMA and 25 wt% MPEGMA, while on terpolymers with the other compositions, platelet adsorption and fibrin clot were observed. It was shown that PDMS segment was predominant on these terpolymer surfaces via XPS. Receding contact angles of terpolymers, on which no platelet was observed, showed intermediate values between PDMS- and MPEG-rich surfaces. It was suggested that these terpolymers had blood compatibility.     

The photolysis of copolymers of methyl methacrylate and methyl acrylate

The photolysis of copolymers of methyl acrylate and methyl methacrylate, covering the entire composition range, is studied with the copolymers in the form of film and in solution, under vacuum and in an atmosphere of oxygen. In film under vacuum, copolymers with high acrylate contents become insoluble, and cross-linking and chain scission may be separated by application of the Charlesby-Pinner equation to sol-gel separation data. Otherwise, the polymer remains soluble, chain scission predominates and may be measured by the changes in number average molecular weight. Differences in the characteristics of chain scission under the four sets of conditions are accounted for in terms of physical factors, such as glass transition temperatures and “cage” recombination of radicals, and chemically in terms of the alternative reactions available to the primary radicals involved.     

Free-radical propagation rate coefficients for cyclohexyl methacrylate,glycidyl methacrylate and 2-hydroxyethyl methacrylate homopolymerizations

Propagation rate coefficients (k_p) for the homopolymerization of cyclohexyl methacrylate (CHMA), glycidyl methacrylate (GMA) and 2-hydroxyethyl methacrylate (HEMA) were determined by the pulsed laser polymerization (PLP)/size-exclusion chromatography (SEC) technique. Temperature was varied between −10 and 90°C and pressure up to 2500 bar. k_p values for CHMA and GMA agree within the experimental accuracy of ± 20 per cent. They are by about a factor of 2.5 below k_p of HEMA. The activation energies and activation volumes of k_p of methacrylates studied so far, including linear and branched alkyl methacrylates, are close to each other: E_A(k_p) = (22 ± 2) kJ · mol⁻¹ and ΔV^≠(k_p) = −(16 ± 2) cm³ · mol⁻¹, respectively, indicating a pronounced family-type behavior.