HO CH2 Research Articles

Vapor Pressure, Vaporization Enthalpies, Critical Parameters, and Heat Capacities of Alkyl Glycolates

Developing biotechnological methods to produce glycolic acid and alkyl glycolates requires knowledge of thermophysical and thermodynamic data. Vapor pressures of linear alkyl glycolates HO–CH2–COO–...

Vinyl ether‐based polyacetal polyols with various main‐chain structures and polyurethane elastomers prepared therefrom: Synthesis, structure, and functional properties

ABSTRACTNovel acid degradable polyacetal polyols and polyacetal polyurethanes able to controlled acid degradation were developed. Polyacetal polyols with various main‐chain structures were synthesized by polyaddition of various vinyl ethers with a hydroxyl group [4‐hydroxy butyl vinyl ether (CH2CHOCH2CH2CH2CH2OH), 2‐hydroxy ethyl vinyl ether (CH2CHOCH2CH2OH), diethylene glycol monovinyl ether (CH2CHOCH2CH2OCH2CH2OH), and cyclohexanedimethanol monovinyl ether (CH2CHOCH2C6H10CH2OH)] with p‐toluenesulfonic acid monohydrate (TSAM) as a catalyst in the presence of the corresponding diols [1,4‐butandiol (HOCH2CH2CH2CH2OH), ethylene glycol (HOCH2CH2OH), diethylene glycol (HOCH2CH2OCH2CH2OH), and 1,4‐cyclohexanedimethanol (HOCH2C6H10CH2OH)], respectively. Polyacetal polyurethanes were prepared by a two‐step polymerization, using the synthesized polyacetal polyols, 4,4′‐diphenylmethane diisocyanate (MDI), and 1,4‐butandiol (BD) as a chain extender. Depending on the main‐chain structures, these polyurethanes had different glass transition temperature (from −44 to 19 °C) and properties such as hydrophobic or hydrophilic. Polyurethanes containing the hydrophilic main‐chain exhibited the thermoresponsiveness and had the certain volume phase transition temperature (VPTT). The polyacetal polyurethanes were flexible elastomers around room temperature (∼25 °C) and thermally stable (Td ≥ 310 °C) and additionally exhibited smooth degradation with a treatment of aqueous acid in THF at room temperature to give the corresponding raw material diols. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44088.

A new intermediate in the Prins reaction.

Two Prins reactions were investigated by the use of DFT calculations. A model composed of R–CH=CH2 + H3O+(H2O)13 + (H2C=O)2, R = Me and Ph, was adopted to trace reaction paths. For both alkenes, the concerted path forming 1,3-diols was obtained as the rate determining step (TS1). TS stands for a transition state. From the 1,3-diol, a bimolecular elimination (TS2) leads to the allylic alcohol as the first channel. In the second channel, the 1,3-diol was converted via TS3 into an unprecedented hemiacetal intermediate, HO–CH2–O–CH(R)–CH2–CH2–OH. This intermediate undergoes ring closure (TS4), affording the 1,3-dioxane product. The intermediate is of almost the same stability as the product, and two species were suggested to be in a state of equilibrium. While the geometry of TS1 appears to be forwarded to that of a carbocation intermediate, the cation disappeared through the enlargement of the water cluster. Dynamical calculations of a classical trajectory using the atom-centered density matrix propagation molecular dynamics model on the four TSs were carried out, and results of IRC calculations were confirmed by them.

On the Effect of Alkyl End Group in Poly(ϵ-caprolactone) Oligomers: Preparation and Characterization

Poly(ϵ-caprolactone) (PCL) oligomers with α-hydroxyl-ω-alkyl end groups (alkyl =–CH2–[CH2–CH2]m–CH3, where m = 1, 2, 4, 5, 6, 7, 8, 9, and 10) were synthesized by ring-opening polymerization (ROP) of ϵ-caprolactone (CL) catalyzed by ammonium decamolybdate (NH4)8[Mo10O34] and using aliphatic primary alcohols as initiators (HO–CH2–[CH2–CH2]m–CH3, where m = 1, 2, 4, 5, 6, 7, 8, 9, and 10). The characterizations of the PCL oligomers were determined by MALDI-TOF, GPC, FT-IR, SAXS and 1H and 13C NMR. The effects of alkyl end groups on thermal properties of the PCL oligomers were analyzed by DSC and TGA.

A Simple and Rapid Preparation of Poly(Glycolide) (PGA) Oligomers Catalyzed by Decamolybdate Anion in the Presence of Aliphatic Alcohols

Poly(glycolide) (PGA) oligomers were obtained by ring-opening polymerization (ROP) of glycolide (GA) catalyzed by ammonium decamolybdate (NH4)8[Mo10O34] and using aliphatic primary alcohols as initiators/chain transfer agents (HO‒CH2‒[CH2‒CH2]m‒CH3, where m = 1, 2, 4, 5, 6, 7, 8, 9, and 10). High yield (85–95%) and short reaction time (15 min) were observed. The characterization of PGA oligomers was determined by 1H and 13C NMR, FT-IR, and DSC.

Study on the influence of teos–diol molar ratio on their chemical interaction during the gelation process

Hybrid organic–inorganic materials, silica–diol, were synthesized by the sol–gel process from mixtures of tetraethylorthosilicate (TEOS) and diols: ethylene glycol (HO–CH2–CH2–OH) and 1,3 propane diol (HO–CH2–CH2–CH2–OH), in acid catalysis. The gels have been synthesized for a molar ratio H2O:TEOS = 4:1 and different molar ratios diol/TEOS: 0.25; 0.5; 0.75; 1.0; 1.25 and 1.5. The resulting gels were studied by thermal analysis and FT-IR spectroscopy, in order to evidence the interaction of diols with silica matrix. Thermal analysis indicated that the condensation degree increases with the molar ratio diol/TEOS until a certain value. The thermal decomposition of the organic chains bonded within the silica network in the temperature range 250–320 °C, leaded to a silica matrix with modified morphology. The adsorption–desorption isotherms type is different for the samples with and without diol. Thus, the specific surface areas have values 200 m2/g for the samples with diols, depending on the annealing temperature.

The 1.3 Å crystal structure of a novel endo‐β‐1,3‐glucanase of glycoside hydrolase family 16 from alkaliphilic Nocardiopsis sp. strain F96

The 1.3 A crystal structure of a novel endo-b-1,3-glucanase of glycoside hydrolase family 16 from alkaliphilic Nocardiopsis sp. strain F96 Guntur Fibriansah, Sumiko Masuda, Naoya Koizumi, Satoshi Nakamura, and Takashi Kumasaka* 1 Department of Life Science, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8501, Japan 2 Department of Bioengineering, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8501, Japan

Preparation and characterization of chitosan‐graft‐poly (ϵ‐caprolactone) with an organic catalyst

AbstractChitosan‐graft‐poly(ϵ‐caprolactone) was prepared via the ring‐opening graft polymerization of ϵ‐caprolactone (CL) through chitosan with 4‐dimethylaminopyridine as a catalyst and water as a swelling agent. The graft content of PCL within the graft copolymer was adjusted by the feed ratio of CL to chitosan, and the highest grafting concentration of PCL was up to about 400%. Fourier transform infrared, 1H NMR, and two‐dimensional heteronuclear single quantum coherence analyses indicated that the amino group (NH2CH‐2) of chitosan initiated the graft polymerization of CL through the backbone of chitosan, and the hydroxyl group (HOCH2–6) of chitosan did not participate in initiating the graft polymerization. The percentage of amino groups initiating the graft polymerization decreased with an increasing molar ratio of CL to chitosan in the feed, and this was attributed to the fact that the graft polymerization system increasingly became heterogeneous with an increasing feed ratio of CL to chitosan. The physical properties of the graft copolymers were characterized by thermogravimetric analysis and wide‐angle X‐ray diffraction, respectively. These suggested that the introduction of PCL grafts through the chitosan backbone would to some extent destroy the crystalline structure of chitosan, and the PCL grafts existed in an amorphous structure. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5353–5361, 2006

Gas-Phase Halide Affinity of Aliphatic Alcohols Estimated by the Kinetic Method

The chloride affinity of ethanol was determined by the kinetic method by examining the dissociation of the [EtOH—Cl—HOR]− dimers (ROH=methanol, 1-propanol, 2-propanol and tert-butanol), generated in the ion source of a triple quadrupole mass spectrometer using chloroform as the chemical ionization reagent. Dimer mass selection and collision-induced dissociation using argon furnished, as products, the two individual alcohol–chloride anionic complexes, i.e. [EtOH+Cl]− and [ROH+Cl]−. The natural logarithm of the ratio of their abundances, i.e. ln ([ROH+Cl]–/[EtOH+Cl]−), correlated linearly with the experimental ROH chloride affinity. Using this linear relationship, the chloride affinity of ethanol is determined to be 43±3 kJ mol−1, which is consistent with the literature value of 43.5±8.4 kJ mol−1. From the slope of the kinetic method plot, an effective temperature of 643 ± 25 K was calculated, suggesting the weakly-bound nature of the cluster ions. The validity of the results was confirmed using the extended version of the kinetic method which showed that there is a negligible difference (–0.06 J mol K−1) in the entropy requirements of the two fragmentation channels. It is also demonstrated that this methodology can be applied to estimate the analogous bromide and fluoride affinities of aliphatic alcohols and to estimate halide affinities not previously known. Thus, these cases constitute additional examples of the advantageous application of the kinetic method in the determination of unknown thermochemical properties. Furthermore, in the dissociation of [EtOH—Cl—HO–CH2–CH2–Y]− cluster ions (Y=F, Cl, OMe and Me), a remarkable linear relationship was observed between the natural logarithm of abundance of product ratios, i.e. ln ([Y–CH2–CH2OH+Cl]−/[EtOH+Cl]−) and the electronegativity of the Y substituent. This is ascribed to the inductive effect in stabilizing the charge on chloride in the cluster ion.

Rapid Analysis of Dithiaalkane Diols by HPLC

A reversed‐phase high performance liquid chromatography (HPLC) method has been developed for simultaneous detection of dithiaalkanediols, having the common formula [(HO–CH2–CH2–S)2(CH2) n ] in a homologues series where n = 1–10. Both isocratic and gradient methods were developed, and the latter was found to be suitable for both qualitative and quantitative analysis. The method is simple, specific, and requires only small quantities of chemicals and reagents.

Ab initio calculations of vibrational spectra of 2-methoxy ethanol in the C–H stretching range

Focussing on the range of the C–H stretching vibrations, spectra of 2-methoxy ethanol (HO–CH2–CH2–O–CH3) were calculated at the MP2 level using the 6-31+G(d) basis set. The spectra exhibit a striking dependence on the molecular conformation which can cause shifts of mode frequencies by up to 80 cm−1. Whereas vibrations above 2955 cm−1 are very characteristic for OH in a gauche conformation, the spectral range between 2850–2900 cm−1 is congested by numerous bands and, therefore, seems poorly suited for analytical purposes. In this range, even the unambiguous assignment of modes becomes impossible due to the overlap of symmetric and antisymmetric modes. The range between 2900 and 2955 cm−1 is characterized by a grouping of the bands. The interaction of methoxy ethanol with water lifts this grouping and yields a more uniform distribution. The results are compared to a recent spectroscopic study of oligo(ethylene glycol) films (Dreesen et al., Chem Phys Lett., 2001, 333, 327). For the films in contact with air the characteristic spectral features are well reproduced and changes induced by water are also reflected in the calculations.

Time-of-flight study of the ionic and neutral particles produced by pulsed-laser ablation of frozen glycerol

The emitted particles from pulsed-laser ablation (PLA), λ=193 nm and fluence=88–400 mJ/cm2, of frozen glycerol was examined using time-of-flight mass spectrometry. The data are analyzed using supersonic molecular-beam theory and the result is interpreted using a thermal/fluid-dynamic model. Both intact and fragmented glycerol are emitted in the PLA process at all fluences and their concentration ratio is fluence dependent. Fragmentation occurs predominantly at one of the C–C bonds forming CH2–OH (31 amu) and HO–CH2–CH–OH (61 amu). CH3 is produced at the target which requires the protonation of a CH2 fragment. At fluences higher than 250 mJ/cm2, ions are detected. These ions have very high velocity, >2000 m/s, and their intensity increases with fluences. PLA is thus not suitable for glycerol transfer under these conditions due to fragmentation. The data show that particle emission proceeds as a simple thermal vaporization process at fluences <200 mJ/cm2. Higher fluences will yield a Knudsen layer (KL), which is formed in front of the target surface. For fluences >300 mJ/cm2, particles from the KL go through unsteady adiabatic expansion prior to free flight. Models of particle and ion formation and interaction are proposed and discussed. © 2001 American Institute of Physics.

Intramolecular Nonbonded Interactions Between Oxygen and Group VIA Elements: An Ab Initio Molecular Orbital and Density Functional Theory Investigation of the Structures of HX—CH 2 —COOH (X=S, Se, and Te)

Ab initio molecular orbital and density functional methods have been used to study the potential energy surfaces of the substituted acetic acids HX—CH2—COOH, where X is one of the Group VIA Chalcophiles S, Se, or Te. The various conformers adopted by these compounds provide information regarding the energetic importance of nonbonded $${\text{X}} \cdots {\text{O}}$$ and $${\text{X}}---{\text{H}} \cdots {\text{O}}$$ hydrogen bonding interactions involving oxygen atoms with different hybridizations. Density functional and ab initio molecular orbital methods yield similar structural and energetic trends for these compounds. Calculations show that the structure of the lowest-energy conformer of each of these acids has the X—C—C—O backbone substantially twisted from planarity, similar to that previously observed for the corresponding aldehydes, HX—CH2—CHO. In the twisted acid structures the shortest $${\text{X}} \cdots {\text{O}}$$ distance is within about 0.1 A of the sum of the X and O van der Waals radii, which reduces overcrowding of the lone pairs of electrons on these atoms. In conformers where the heavy atom backbone is planar, one of the $${\text{X}} \cdots {\text{O}}$$ distances is significantly shorter than the sum of the van der Waals radii, and the total molecular energy of these conformers is higher than that of the twisted forms. The variation of X—H vibrational frequencies among conformers reflects the extent of X—H hydrogen bonding, and indicates that formation of this hydrogen bond is not the dominant factor in determining the lowest-energy conformation. When X is oxygen (HO—CH2—COOH), the lowest-energy conformer is also nonplanar, whereas for the corresponding aldehyde, HO—CH2—CHO, the lowest-energy conformer is a planar structure with CS symmetry. The conformational preferences of these simple species provide reference points for inter- and intramolecular interactions in more complex systems of biological interest.

Enzyme-catalysed Transformations of Compounds Containing the -CH2-AsO3H2 Group

Enzymes that act on substrates R–O–PO3H2 often work on substrate analogues R–O–AsO3H2; such substrates are unstable, since esters of H3AsO4 hydrolyse easily. They also form easily, so that an enzyme that acts on R–O–PO3H2 often acts on a mixture of R–OH and arsenate via an ester that forms at the active site. Similarly coenzyme analogues may be formed; for example, a stable and active aspartate aminotransferase forms from the apoenzyme with free pyridoxal and arsenate. Enzymes that convert R–O–PO3H2 into a diester often act on R–CH2–AsO3H2, a stable substrate analogue; then the product is unstable and hydrolyses to re-form the analogue, giving a futile cycle. For example, RNA polymerase acquires exonuclease activity in the presence of H2O3P–CH2–AsO3H2; adenylate kinase acquires ATPase activity in the presence of the arsonomethyl analogue of AMP. A recent observation is that HO–CH2–CHOH–CH2–CH2–AsO3H2 is a good substrate for glycerol-3-phosphate dehydrogenase. The product is unstable and eliminates arsenite, sharing this ability with other 3-oxoalkylarsonates. Thus this enzyme–catalysed oxidation is a lethal synthesis, in view of the toxicity of arsenite. Another unusual biochemical reaction of an arsonic acid is seen in the ability of a bacterium to use arsonoacetate as its sole source of carbon and energy. In contrast with the elimination of arsenite by 3-oxoalylarsonic acids, 3-oxoalkylphosphonic acids, R–CO–CH2–CH2–PO3H2, are stable. 2-Oxoalkylphosphonic acids, R–CO–CH2–PO3H2, however, are moderately unstable to hydrolysis, yielding phosphate and R–CO–CH3. 2-Oxoalkylarsonic acids, R–CO–CH2–AsO3H2, decompose in the same way, but much more readily, yielding arsenate. © 1997 by John Wiley & Sons, Ltd.

The isomers of ionized dimethyl sulfoxide (C2H6OS+·) and their CH3OS+ fragments. An ab initio and multiple‐stage mass spectrometric (MSn) study

AbstractThe relative stabilities, isomerizations and dissociations of ionized dimethyl sulfoxide (DMSO), its three C2H6OS+· isomers and of all their 14 conceivable CH3OS+ fragments (1–14), have been investigated by ab initio calculations at the MP2/6–31G(d,p)//6–31G(d,p) + ZPE and G2 levels of theory, and by multiple‐stage two‐ and three‐dimensional mass spectrometry performed in a pentaquadrupole instrument. The ab initio relative energies of the isomers, their connecting transition states, and their dissociation thresholds were used to elaborate potential energy surface diagrams that precisely corroborate and unify several previously divergent experimental observations on these systems. The most kinetically favorable isomerization of (CH3)2SO+· (I) to its aci‐form CH2S(OH)CH (II) displays a transition state considerably lower in energy than the threshold for its direct dissociation by CH3⋅ loss. Therefore, low‐energy, long‐lived metastable ions I are predicted to isomerize to II, and to dissociate in turn to CH2S+OH (2) upon CH3⋅ loss. Ions I excited a few electronvolts above the threshold are, on the other hand, predicted to dissociate directly to CH3S+O (1). Isomerization of I to the most stable C2H6OS+· ion, that is CH3SOCH (III), displays the most energetic transition state and should be negligible, whereas III is predicted to dissociate by CH3⋅ loss preferentially to 1 rather than 5 (CH3OS+). Nine CH3OS+ isomers, that is 1, 2, (HCS…OH2)+ (3), +CH2S(O)H (4), 5, HC(SH)OH+ (9), CH2OSH+ (10), CH2+OSH (11), and (HCO…SH2)+ (14), were found as true minima on the RHF/6–31G(d,p) potential‐energy surface, and some of their isomerization barriers and dissociation thresholds were estimated. Tandem and multiple‐stage (MS3) mass spectrometric experiments show that non‐dissociating DMSO+· ions produce, upon collision‐induced dissociation (CID), a mixture of approximately 40% of 1 and 60% of 2, whereas the CID chemistry of 1 and 2 is affected considerably by the collision energies employed. Both the experimental and theoretical results on 1 and 2 allow a detailed interpretation of their complex dissociation chemistry, which clarifies the nature of most of their indirect fragments. Such fragments are proposed to be formed via the common isomerization/dissociation sequences 1 → 2 → 9 ⇌ 3 → HCS+ (m/z 45) + H2O, and 1 → 2 → [7, HOCH2S+] → S + CH2OH+ (m/z 31). These processes are favored at lower collision energies, whereas direct dissociation of 1 to CH3+ (m/z 15) and SO+· (m/z 48), and of 2 to CH2S+· (m/z 46) occurs to greater extents at higher collision energies.

The [CH5NO]+ ˙ potential energy surface: Distonic ions, lon‐dipole complexes and hydrogen‐bridged radical cations

AbstractBy combining results from a variety of mass spectrometric techniques (metastable ion, collisional activation, collision‐induced dissociative ionization, neutralization‐reionization spectrometry, 2H, 13C and 18O isotopic labelling and appearance energy measurements) and high‐level ab initio molecular orbital calculations, the potential energy surface of the [CH5NO]+ ˙ system has been explored. The calculations show that at least nine stable isomers exist. These include the conventional species [CH3ONH2]+ ˙ and [HOCH2NH2]+ ˙, the distonic ions [OCH2NH3]+ ˙, [ONH2CH3]+ ˙, [CH2O(H)NH2]+ ˙, [HONH2CH2]+ ˙, and the ion‐dipole complex CH2NH2+ …︁ OH˙. Surprisingly the distonic ion [CH2ONH3]+ ˙ was found not to be a stable species but to dissociate spontaneously to CH2O + NH3+ ˙. The most stable isomer is the hydrogen‐bridged radical cation [HCO …︁ H …︁ NH3]+ ˙ which is best viewed as an immonium cation interacting with the formyl dipole. The related species [CH2O …︁ H …︁ NH2]+ ˙, in which an ammonium radical cation interacts with the formaldehyde dipole is also a very stable ion. It is generated by loss of CO from ionized methyl carbamate, H2NC(O)OCH3 and the proposed mechanism involves a 1,4‐H shift followed by intramolecular ‘dictation’ and CO extrusion. The [CH2O …︁ H …︁ NH2]+ ˙ product ions fragment exothermically, but via a barrier, to NH4+ ˙ HCO…︁ and to H3NC(H)O+ ˙ H˙. Metastable ions [CH3ONH2]+…︁ dissociate, via a large barrier, to CH2O + NH3+ + and to [CH2NH2]+ + OH˙ but not to CH2O+ ˙ + NH3. The former reaction proceeds via a 1,3‐H shift after which dissociation takes place immediately. Loss of OH˙ proceeds formally via a 1,2‐CH3 shift to produce excited [ONH2CH3]+ ˙, which rearranges to excited [HONH2CH2]+ ˙ via a 1,3‐H shift after which dissociation follows.

Native ethylene glycol in wine: Application of a dead volume free, very fast “deans heart‐cut” system on‐line with multi‐chromatography

AbstractData about the existence of native HOCH2CH2OH (MEG) in natural wines and champagne has led to delicate questions because of legal decisions already made to declare wine or champagne illegal for sale if the MEG concentrations found are above 10 mg/liter. Action has been taken because of the DEG (diethylene glycol) disaster in European wines of 1985…86. An incorrect legal decision was made due to the belief that MEG cannot be produced biochemically by grape vines. A further reason may be lack of correct data on native MEG trace concentrations, as a result of the special behavior of this diol. As first member of a homologous series whose higher members (C4) are normally found in all wines at quite high concentration levels, MEG shows extremely adsorptive behavior. The solution of the chromatographic problems is summarized in this paper. MEG concentrations in Riesling as example are in the range of 2 to 6 mg/liter and can easily be increased by biotechnological steps to a level of around 10 to 60 mg/liter. This is again due to the specific adsorptive behavior of MEG, which can be enriched on filter surfaces and displaced when the wine acidity changes with changing types. In order to control and guarantee the qualitative and quantitative results of MEG analyses we used a combination of Deans heart cutting on‐line with Multi‐Chromatography. It was easy to produce false data by many otherwise useful single column or two‐dimensional separation processes, etc.

New telechelic polymers and sequential copolymers by polyfunctional initiator‐transfer agents (inifers). VII. Synthesis and characterization of α,ω‐di(hydroxy)polyisobutylene

AbstractA new telechelic polyisobutylene diol, HOCH2PIBCH2OH, carrying two terminal primary hydroxyl end groups has been prepared from α,ω‐di(isobutenyl)polyisobutylene, CH2C(CH3)‐ CH2PIBCH2C(CH3)CH2, by regioselective hydroboration followed by alkaline hydrogen peroxide oxidation. Infrared (IR) spectra, 1H‐NMR analysis of the pure and silylated products, and ultraviolet (UV) spectra of phenylisocyanate‐treated diols indicate quantitative yields and two CH2OH termini per polyisobutylene chain. The viscosity of HOCH2PIBCH2OH is higher than that of the starting α,ω‐diolefin. The telechelic diol prepolymer opens new avenues to the synthesis of many new materials, e.g., polyurethanes.

Hydroxyl radical-induced oligomerization of ethylene in deoxygenated aqueous solution

Deoxygenated aqueous solutions of ethylene (4 × 10–3M) and nitrous oxide (9 × 10–3M) were irradiated with γ-60Co rays at dose rates of 2.6 × 1015 and 2.1 × 1016 eVg–1s–1. The most prominent among the 19 products determined are butane-1,4-diol, hexane-1,6-diol, and octane-1,8-diol. A satisfactory material balance with respect to primary water radicals was obtained. In the radiolysis of N2O-containing water the major part (ca. 90%) of the primary radicals are OH radicals which are scavenged by ethylene to give β-hydroxyethyl radicals. These radicals either combine, butane-1,4-diol being the product [reaction (i)], or add to ethylene [reaction (ii)]. The 2HO–CH2–ĊH2→ HO–CH2–(CH2)2–CH2OH (i), HO–CH2–ĊH2+ CH2CH2→ HO–CH2–(CH2)2–ĊH2(ii) self-termination rate constant has been measured by pulse radiolysis [2k(i)=(5 ± 2)× 108 l mol–1s–1]. The propagation rate constant [k(ii)=(3 ± 2)× 104 l mol–1s–1] has been derived from the dose rate dependence of G(diols) by computer-aided fitting. The β-hydroxyethyl radicals are readily oxidized by copper(II) ions (5 × 10–3M). The major product is ethylene oxide [reaction (iii)], and little (ca. 3%) ethylene glycol is formed [reaction (iv)]. HO–CH2–ĊH2+ Cu2+→ [graphic omitted] + Cu++ H+(iii), HO–CH2–ĊH2+ Cu2++ H2O → HO–CH2–CH2–OH + Cu++ H+(iv)

Relaxation behavior of polymethacrylamide and polyacrylamide and of their copolymers with 2-hydroxyethyl methacrylate

Abstract A free-oscillating torsional pendulum was used to investigate the effect of the concentration of the HO—CH2—CH2—COO— and NH2 CO— side chains and α-methyl groups of the main chains on the mechanical relaxation behavior of polymethacrylate and polyacrylate polymers and copolymers in the glassy state. The intensity of the low-temperature (γ) dispersion is linearly proportional to the volume fraction of 2-hydroxyethyl methacrylate (HEMA) in both series of copolymers and is independent of the content of the α-methyl groups. The temperature of the γ-dispersion, which for PHEMA is about —133°C (1 Hz), is lowered by the incorporation both of methacrylamide (MAAm) and—although to a lesser extent—of acrylamide (AAm) units. The secondary (β1) process of PHEMA (28°C; 1 Hz) is shifted toward higher temperature with increasing amount of MAAm, so that for the dry PMAAm it cannot be observed at temperatures up to 120°C. On the other hand, PAAm is characterized by the secondary relaxation at —25°C (1 Hz); however...