Mechanisms of Action of (Meth)acrylates in Hemolytic Activity, in Vivo Toxicity and Dipalmitoylphosphatidylcholine (DPPC) Liposomes Determined Using NMR Spectroscopy

We investigated the quantitative structure-activity relationships between hemolytic activity (log 1/H(50)) or in vivo mouse intraperitoneal (ip) LD(50) using reported data for α,β-unsaturated carbonyl compounds such as (meth)acrylate monomers and their (13)C-NMR β-carbon chemical shift (δ). The log 1/H(50) value for methacrylates was linearly correlated with the δC(β) value. That for (meth)acrylates was linearly correlated with log P, an index of lipophilicity. The ipLD(50) for (meth)acrylates was linearly correlated with δC(β) but not with log P. For (meth)acrylates, the δC(β) value, which is dependent on the π-electron density on the β-carbon, was linearly correlated with PM3-based theoretical parameters (chemical hardness, η; electronegativity, χ; electrophilicity, ω), whereas log P was linearly correlated with heat of formation (HF). Also, the interaction between (meth)acrylates and DPPC liposomes in cell membrane molecular models was investigated using (1)H-NMR spectroscopy and differential scanning calorimetry (DSC). The log 1/H(50) value was related to the difference in chemical shift (ΔδHa) (Ha: H (trans) attached to the β-carbon) between the free monomer and the DPPC liposome-bound monomer. Monomer-induced DSC phase transition properties were related to HF for monomers. NMR chemical shifts may represent a valuable parameter for investigating the biological mechanisms of action of (meth)acrylates.     

The polymerization and copolymerization of nitroalkyl acrylates and nitroalkyl methacrylates

Nitroalkyl acrylates and methacrylates involving some new compounds were prepared. The homopolymerization of these monomers in toluene and their copolymerization with styrene in acetone were carried out with azobisisobutyronitrile as initiator. The rate of polymerization of the nitroalkyl acrylates showed a correlation with the number of nitro groups situated on the ester side chain. The apparent activation energies of the polymerization were found to be 22.0–27.5 kcal./mole for the nitroalkyl acrylates and about 11.5–13.0 kcal./mole for the nitroalkyl methacrylates. From the reactivity ratios and Q-e values of the copolymerization the following information was obtained. The copolymerization behavior of nitroalkyl acrylates and methacrylates showed an alternating tendency, and these monomers belong to the conjugative monomer groups. On the reactivities of these monomers, the polarity of vinyl group was affected a little by nitro group of ester bond side, and the resonance affected little. These monomers were crosslinked with 2-methyl-2-nitro-1,3-propylene diacrylate. Some of the polymers showed marked improvement in the physical properties of elastomers.     

Synthesis and polymerisation of new multifunctional urethane methacrylates

New multifunctional urethane methacrylates were synthesised by addition of methacrylates containing a hydroxy group, such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate or glycerol dimethacrylate, to α,α,α′,α′-tetramethyl-m-xylylene diisocyanate. The structure of the new monomers was confirmed by IR, ¹H NMR and ¹³C NMR spectroscopy. The photopolymerisation of the crosslinking monomers in bulk using camphorquinone as photoinitiator results in transparent, crosslinked polymers.     

Thermoresponsive poly(oligo ethylene glycol acrylates)

Thermoresponsive polymers have been the subject of numerous publications and research topics in the last few decades mostly driven by their easily controllable temperature stimulus and high potential for in vitro and in vivo applications. P(NIPAAm) is the most studied amongst these polymers, but recently other types of polymers are increasingly being investigated for their thermoresponsive behavior. In particular, polymers bearing a short oligo ethylene glycol (OEG) side chain have been shown to combine the biocompatibility of polyethylene glycol (PEG) with a versatile and controllable LCST behavior. These polymers can be synthesized via controlled radical polymerization techniques from various monomers consisting of an OEG chain and a polymerizable group like a (meth)acrylate, styrene or acrylamide. OEG acrylates offer significant advantages over, e.g., OEG methacrylates as the lower hydrophilicity of the backbone facilitates thermoresponsive behavior with smaller, more defined side chains. Furthermore, PEG acrylates can be polymerized using all major controlled radical polymerization techniques, unlike OEG methacrylates. This review will focus on OEG acrylate based (co)polymers and will provide a comprehensive overview of their reported thermoresponsive properties. The combination and comparison of this data will not only highlight the potential of these monomers, but will also serve as a starting point for future studies.     

Carbon nuclear magnetic resonance characterization of ethylene-propylene-1-octadecene terpolymers and comparison with ethylene-propylene-1-hexene and 1-decene terpolymers

In this paper, we report the complete ¹³C NMR characterization of a set of ethylene-propylene-1-octadecene terpolymers obtained with the metallocenic system rac-ethylene bis-indenyl zirconium dichloride, using different comonomer ratios. A detailed study of ¹³C NMR chemical shifts, triad sequence distributions, monomer average sequence lengths and reactivity ratios for these terpolymers is presented. The incorporations of 1-octadecene were superior of those obtained using 1-hexene and 1-decene in the same conditions. Catalytic activities of terpolymers of ethylene-propylene and α-olefins (α-olefins:1-hexene, 1-decene and 1-octadecene) were compared showing that they increase with the amount of propylene in the feed.     

Transport of gases and vapors in methacrylic copolymers of varying side chain length

The gas transport properties of copolymers of dodecyl methacrylate with ethyl methacrylate and hydroxypropyl methacrylate have been studied. The diffusion, solubility and permeability of oxygen, nitrogen, carbon dioxide, methane, ethane and ethylene have been measured in the temperature range 0-50 °C, and activation energies and heats of solution have been obtained. A comparison with the data available in the literature on acrylates and other methacrylates of varying aliphatic side chain length has been performed. The diffusion coefficient of gases increases with the side chain length in a way similar to that found for homologous acrylates. A representation of log(D) as a function of the inverse of the fractional free volume shows that all acrylates and methacrylates of lineal alkyl side chain fall on the same straight line.     

Concentration effects in the base-catalyzed hydrolysis of oligo(ethylene glycol)- and amine-containing methacrylic monomers

Concentration effects in the base-catalyzed hydrolysis of water-soluble methacrylates (3-(N,N-dimethylaminoethyl) methacrylate (DMAEMA), 2-hydroxyethyl methacrylate (HEMA) and oligo(ethylene glycol) methacrylates (OEGMAs)) have been studied. These monomers are rapidly hydrolyzed in the presence of bases at the room temperature in dilute aqueous solutions, but the reaction rate decreases sharply in highly concentrated solutions. A clear correlation was found between a form of the viscosity isotherm for DMAEMA solutions and the concentration dependence of the autocatalytic hydrolysis rate which indicates the connection of process kinetics with the structure of solutions. These data should be considered when carrying out homo- and copolymerization of the previously mentioned monomers in aqueous solutions.     

Chiral α substituted acrylates side-chain polymers with a cinnamate core

Summary In this paper we report thermal studies and microscopic observations on optically active liquid crystalline monomers having the following general formula: with X = H (acrylates), CH₃ (methacrylates) and Cl (chloroacrylates) and n=2, 6, 11 (flexible spacer groups) and a few corresponding side-chain polymers.     

Synthesis and photopolymerization of phosphonic acid monomers for applications in compomer materials

Novel methacrylate monomers bearing phosphonic acid groups 1 and 2 as well as new sulfur methacrylates 9 and 10 have been prepared in good yields from thiophenol. They have been fully characterized by ¹H‐NMR, ¹³C‐NMR, ³¹P‐NMR, and HRMS. Their copolymerization with a bis‐GMA : TEGDMA (1 : 1) blend has been investigated with photodifferential scanning calorimetry at 50°C with camphorquinone as a photoinitiator and ethyl 4‐(dimethylamino)benzoate (EDAB) as a coinitiator. The higher the content of acidic monomer 1 or 2 incorporated in the bis‐GMA : TEGDMA (1 : 1) blend, the lower the mixtures reactivity. The phosphonic acid group has been proved to be responsible for this drop of reactivity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Linking chemical reactivity and protein precipitation to structural characteristics of foliar tannins

Tannins influence ecosystem function by affecting decomposition rates, nutrient cycling, and herbivory. To determine the role of tannins in ecological processes, it is important to quantify their abundance and understand how structural properties affect reactivity. In this study, purified tannins from the foliage of nine species growing in the pygmy forest of the northern California coast were examined for chemical reactivity, protein precipitation capacity (PPC), and structural characteristics (¹³C NMR). Reactivity of purified tannins varied among species 1.5-fold for the Folin total phenol assay, and 7-fold and 3-fold, respectively, for the acid butanol and vanillin condensed tannin assays. There was about a 5-fold difference in PPC. Variation in chemical reactivity and PPC can be largely explained by differences in structural characteristics of the tannins determined by ¹³C NMR. In particular, the condensed versus hydrolyzable tannin content, as well as the hydroxylation pattern of the B-ring and stereochemistry at the C-2–C-3 position appear to influence reactivity. Due to the large differences in chemical reactivity among species, it is necessary to use a well-characterized purified tannin from the species of interest to convert assay values to concentrations. Our results suggest that structural characteristics of tannins play an important role in regulating their reactivity in ecological processes.     

Radical copolymerization of higher alkyl methacrylates with acrylic esters and amides in toluene: influence of monomer association on copolymer composition

A strong concentration effect was found in a course of copolymerization of higher N-alkylacrylamides with higher alkyl acrylates in toluene, where the fraction of amide functions in copolymers obtained at low degrees of conversion decreases significantly with an increase in total concentration of monomers in solution. It was established that the observed effect is independent of the structure of alkyl substitutes for both types of monomers. The data gathered with the aid of IR spectroscopy and computer modeling show that this concentration effect relates to the formation of amide associates in solution. The concentration effect was absent for the copolymerization of higher alkyl methacrylates and higher alkyl acrylates.     

Copolymerization and Dark Polymerization Studies for Photopolymerization of Novel Acrylic Monomers

The copolymerization behavior and the dark polymerization kinetics of highly reactive novel acrylic monomers were compared to traditional acrylate monomers. Copolymerization of thiol functionalities with novel acrylic monomers was characterized, and it was observed that the inclusion of secondary functionalities such as carbamates, carbonates, and cyclic carbonates, in acrylic monomers significantly alters the relative reactivity of the novel acrylates with thiols. While traditional aliphatic acrylates exhibited propagation to chain transfer ratios ranging between 0.8 (±0.1) and 1.5 (±0.2), the novel acrylates characterized by secondary functionalities exhibited much higher propagation to chain transfer ratios ranging from 2.8 (±0.2) to 4 (±0.2). In the dark polymerization studies, the kinetics of the novel acrylates were evaluated following cessation of the UV light. The novel acrylates exhibited extensive polymerization in the dark compared to most traditional acrylates and diacrylates. For instance, cyclic carbonate acrylate was observed to attain 35% additional conversion in the dark when the UV light was extinguished at 35% conversion, whereas traditional acrylates such as hexyl acrylate attained only 3% additional conversion when the UV light was extinguished at 35%, and a diacrylate such as HDDA attained 15% additional conversion when the UV light was extinguished at 40% conversion. Also, through choice of appropriate monomers, the dark polymerization studies were performed such that the polymerization rate was approximately the same at the point the light was extinguished for all these monomers. The copolymerization and dark polymerization studies support the hypothesis that the nature of the propagating species in the novel acrylates is altered as compared to traditional acrylic monomers and polymerizations.     

Controlled synthesis of azobenzene functionalized homo and copolymers via direct acyclic diene metathesis polymerization

A powerful and efficient strategy for obtaining a series of azobenzene functionalized linear unsaturated polyolefins is described, which involves the first design and synthesis of three different α,ω-diene monomers with different reactivity of acrylates and terminal double bonds and their subsequent acyclic diene metathesis (ADMET) polymerization under mild reaction conditions. Different ruthenium based metathesis catalysts and conditions were tested to optimize the ADMET polymerization of these monomers. Besides, this polycondensation method is also reported allowing for the synthesis of alternating and diblock azobenzene-containing copolymers with molecular weight control by using the selectivity of olefin cross-metathesis between acrylates and terminal olefins. The resulting polymers showed well-defined molecular weights, reasonable polydispersity index, and reversible photoresponsive behavior. This special combination of the benefits of metathesis polymerization and azobenzene is a highly versatile system for materials in many applications.     

Kinetic study of addition of substituted and unsubstituted phenylthiyl radicals to aromatic olefins: Steric effect on reactivities of monomers containing bulky groups

For olefins containing aromatic groups such as naphthyl, monomer reactivities have been evaluated on the basis of the absolute rate constants and relative equilibrium constants which were determined by the flash photolysis method using phenylthiyl radicals as attacking radicals. The rate constant for addition of α-methyl-1-vinylnaphthalene is lower than that of α-methyl-2-vinylnaphthalene. This suggests that the aromatic π-orbital; of the 1-naphthalene derivative are twisted away from the olefinic π-orbital; in the transition state, the delocalization of the unpaired electron on the olefinic carbon into the naphthyl group is reduced by the angular structure. For such twisted monomers, the dihedral angles between the aromatic π-orbitals and the olefinic π-orbital have been estimated by comparing the observed rate constants with the reactivity indexes calculated by the molecular orbital method. In the case of α,β-disubstituted olefins, the rate constants are lower than those of α,α-disubstituted ones; this suggests that the approach of the phenylthiyl radical is impeded. New reactivity parameters were evaluated for the monomers with bulky groups.     

Complete Assignment of 1H and 13C NMR Spectra of Benz[a]Anthracene-7,12-dione and its Nitro Derivative

Benz[a]anthracene-7, 12-dione (1) was nitrated directly by nitric acid and a nitro-derivative (2) was obtained. Molecular orbital calculation predicted that the nitration reaction occurs in the C1 or C4 position of (1). To determine the position of the nitro group of (2), NMR chemical shifts were used. The absence of the chemical shift at δ9.7 in (2) clearly indicated that the nitro substituent issituated at the C1 position. The methodologies of FG-HOHAHA, FG-NOESY, FG-CH-COSY, and FG-HMBC were also used for detailed NMR spectral determination for their polycyclic aromatic ketons.     

The alkaline hydrolysis of methacrylates

The hydrolysis of a number of methacrylates in a 2,5% water-alcoholic solution of sodium hydroxide at 25°C was investigated. The hydrolysis of the ester group in 2-(N-methylanilino)ethyl(III), 3- and 4-dimethylaminobenzyl-(IV, V)-2-carboxyphenyl (VI) and 2,2,2-trichloroethyl (VII) methacrylate proceeded at approximately the same rate as in methyl methacrylate (I) and dimethylaminoethyl methacrylate (II); within 25 min, some 80% of the original esters were hydrolyzed. In alkaline solutions of 1,2,2,2-tetrachloroethyl (VIII), 2-(1,2,2,2-tetrachloroethoxy)ethyl (IX) and 1-(4-chlorophenyl)-2,2,2-trichloroethyl(X) methacrylates, the rate of hydrolysis of the ester group is decreasing in the order VIII>IX>X. The hydrolysis of the ester group was characterized by the rate constants of second order.     

New Iron(II) Complexes for Atom‐Transfer Radical Polymerization: The Ligand Design for Triazacyclononane Results in High Reactivity and Catalyst Performance

Mononuclear cordinatively unsaturated iron(II) complexes having a triazacyclononane ligand were developed as highly efficient and environmentally friendly catalysts for the atom‐transfer radical polymerization (ATRP). These iron catalysts showed high performance in the well‐controlled ATRP of styrene, methacrylates, and acrylates. The high reactivity of these catalysts led to well‐controlled polymerization and block copolymerization even with lower catalyst concentrations.     

Fluorinated poly(meth)acrylate: Synthesis and properties

Due to good reactivity of fluorinated (meth)acrylates with other monomers or polymer segments, fluorinated poly(meth)acrylates possess more economical and convenient synthesis routes than other fluoropolymers. This feature article initially summarizes different types of fluorinated (meth)acrylates, which can be divided into fluorinated alkyl (meth)acrylates and fluorinated aryl (meth)acrylates. Subsequently, various approaches for synthesizing fluorinated poly(meth)acrylates including random, block, graft or star copolymers are described. Conventional free radical polymerization can be used in synthesizing random copolymers, while controlled/“living” radical polymerization can provide well-defined copolymers with accurate control over molecular weight and special structures as expected. In particular, introduction of fluorinated components into as-prepared copolymers offers an alternative route to synthesize fluorinated poly(meth)acrylates which are difficult to be obtained directly via polymerization. The incorporation of fluorine can confer unique and highly desirable properties to poly(meth)acrylates such as low surface energy, thermal stability, chemical and weather resistance, low refractive index, and self-organization characteristics. Such properties are described in great details based on many recent articles.     

Solid-State 13C CP/MAS NMR for Alkyl-O-Aryl Bond Determination in Lignin Preparations

Several lignin preparations (Freudenberg lignin, Björkman lignin, and Pepper lignin), technical lignins (soda, soda-AQ, Kraft, Kraft-AQ, and hydrolysis), dimeric lignin model compounds, and different polysaccharides (galactoglucomannan, arabinogalactan, xylan, and arabinan) were analyzed by means of solid-state ¹³C CP/MAS NMR. Signals assignment in solid-state NMR lignin spectra was performed on the basis of the conducted studies and earlier published data. It was established that there exists strong linear correlation (r = 0.985) between Alkyl-O-Aryl inter-unit bond content in lignin and integral signals intensity in NMR spectra in the range of chemical shifts of 96–68 ppm. The integral signals intensity was measured in correlation with the reference integral signals in the range of chemical shifts of 162–102 ppm, typical for aromatic carbon atoms. To eliminate the effect, caused by carbohydrates contained in lignin, the correction factor of 0.67% of the area of integration per 1% of carbohydrates was determined. It was shown that the solid-state ¹³C CP/MAS NMR method allowed to determine Alkyl-O-Aryl bond content in both soluble and insoluble lignin preparations, and also to determine methoxyl groups content in soluble preparations.     

Kinetic studies on lipase-catalyzed acetylation of 2-alkanol with vinyl acetate in organic solvent

Lipase-catalyzed acetylation of 2-alkanol with vinyl acetate has been studied kinetically using Burkholderia cepacia lipase (BCL), enantiomerically pure (R)- and (S)-2-alkanols and different organic solvents. The rate equation was derived by the steady state method for the simplified mechanism. The second order rate constants (k(R) and k(S)) for (R)- and (S)-2-alkanols were evaluated from the slopes of the double reciprocal plots, v(-1) vs. [2-alkanol](-1), where v is the initial rate of the reaction. The log k(R) value increased with the solvent hydrophobicity log P, where P is a partition coefficient of a given solvent between octanol and water. The log k(S) value also increased with log P except the bulky solvents such as 1,4-dioxane and cyclohexane, in which the rates were faster than those expected from the log k(S) vs. log P plot. The slope of log k(S) vs. log P plot was larger than that for (R)-2-alkanol. Thus, log E (E=k(R)/k(S): enantioselectivity) decreased with log P except the bulky solvents. The rate constants and the enantioselectivity were different depending on the structure (carbon number CN) of 2-alkanol. The log E vs. CN plot was minimized at CN=8 and 10 and the log k(S) vs. CN plot maximized at CN=8 and 10. In contrast the log k(R) vs. CN plot showed a different feature from the log E vs. CN plot. These facts suggest that dependence of E on CN is more strongly affected by the reactivity of (S)-2-alkanol than that of (R) isomer in this acetylation.