Hydrolytically stable acidic monomers used in two steps self-etch adhesives

This study deals with the stability of new phosphonic monomers bearing an acrylamide moiety designed to increase the adhesion durability. Synthesis of monomers bearing acrylamide and methacrylate moieties, as well as their use in Self-Etch Adhesives is reported. The adhesion of a degraded methacrylate based adhesive has been evaluated. Homologous self-etching primers containing monomers bearing acrylamide or methacrylate were formulated and used either immediately after formulation or after 18 months. Their adhesive performances were assessed by shear bond strength testing and their degradation measured by NMR, HPLC-MS. While no differences were found in terms of adhesion between fresh and aged acrylamide based adhesive, the instability of methacrylate based ones was demonstrated. Nevertheless, methacrylate based SEAs still have good adhesion abilities. The co-monomer used, N,N′-diethyl-1,3-bis(acrylamido)propane is expected to be responsible for good mechanical properties even for degraded SEAs. Lastly, the stability of acrylamide monomer seems to be of interest in the prospect of developing SEA with longer shelf life.     

THE EFFECT OF SLNGLE AND MIXED MICELLES OF SURFACTANTS ON POLYMERIZATION OF ACRYLAMIDE

Acrylamide is conveniendy polymerized in aqueous solution lo a water soluble polymer. The measurements of kinetic parameters of polymerization of acrylamide, in aqueous and micellar solution, have been earned out by conduction calorimeter. The polymerization is initiated by sodium sulfite and sulfite-persulfate redox system. The effect of initiator and monomer concentration as well as temperature and surfactants on polymerization rale constant has been investigated. The analog thermogram method has been employed to calculate the rate constants. The activation energy is calculated from Arrhenius relationship and molecular weights are determined by viscometry. Rate equations have been derived and reaction mechanism hove been suggested. The rate of reaction is found to increase with temperature and monomer concentration.     

Photoinduced Graft Copolymerization onto Chitosan Under Heterogeneous Conditions

Photoinitiated graft copolymerization of acrylamide onto chitosan under heterogeneous conditions and in the absence of a photo initiator was investigated. The effect of irradiation time, the amount of chitosan and monomer concentration on the extent of grafting was examined. The maximum grafting percentage obtained was 294%. The copolymer was characterized using carbon-13 nuclear magnetic resonance (¹³C-NMR) spectroscopy, X-ray diffraction analysis (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The system designed allows synthesis of grafted chitosan with free amine groups which are otherwise possible only by chemical protection. The swelling properties of copolymer were followed in aqueous solution.     

Preparation of Polymeric Ultraviolet Absorbers and Their Effects on the Photodegradation of Polyethylene

Polymeric ultraviolet absorbers were prepared from 2-hydroxy-4-acryloyloxybenzophenone and 2-hydroxy-4-methacryloyloxybenzophenone and their inhibitive effect for photodegradation of polyethylene were examined by measuring mechanical strength, melt index, carbonyl group, and color difference. The polymeric ultraviolet absorbers were superior to the same type of ultraviolet absorber with low molecular weight in many properties, but inferior to Tinuvin, a commercial reagent, which has a different molecular structure. Therefore, within the ultraviolet absorbers examined, molecular structure seems to be a more important factor than molecular weight.     

SURFACTANT MEDIATED POLYMERIZATION KINETICS OF ACRYLAMIDE USING CR(VI)-CYCLOHEXANONE REDOX SYSTEM

The effect of organized surfactants on the kinetics of acrylamide (AM) polymerization have been studied over a temperature range of 25–45°C using Cr (VI)-cyclohexanone (CH) redox system as initiator. The rate of polymerization, R_p(obs), as well as, the percentage of the monomer conversio were found to be increased with increasing the concentration of the anionic surfactant (SDS), above its CMC. But the cationic surfactant (CTAB) reduced the rate considerably at higher concentration, while non-ionic surfactant (TX-100) played no role on the rate. The effect of [Cr(VI)], [CH], [AM], [H+], and ionic strength on the rates have also been examined. The presence of 0.015M SDS decreased the overall activation energy of the polymerization by 6.28 k.Cal/ mole as compared to that in the absence of a surfactant. On increasing the SDS concentration, the viscosity average molecular weight was also found to increase. For the polymerization process, a mutable mechanistic scheme has been pro-posed.     

STUDY ON COPOLYMERIZATION OF ACRYLAMIDE WITH STYRENE INITIATED BY METHYL ETHYL KETONE AND ITS DERIVATIVES IN COMPARISON WITH CONVENTIONAL RADICAL INITIATOR

Copolymerization of acrylamide (AAm) with styrene (St) was carried out in the presence of methyl ethyl ketone (MEK), methyl isopropyl ketone (MIK) and t-butyl methyl ketone (tBMK) without any conventional initiator in tetrahydrofuran (THF) at 60°C. The copolymerization of AAm with St proceeded readily in the presence of the MEK, MIK, and tBMK, while no copolymerization of AAm with St proceeded in the absence of these ketones under the same conditions and no homo-polymerization of St proceeded even in the presence of the ketones. The reactivity ratio of monomer AAm (r₁) is smaller than that of St (r₂) in all of the copolymerization systems, and increases as the order: MEK < MIK < tBMK. The conversion of the copolymerizations increases as the same order described above. The interaction between AAm and the ketones with hydrogen bonding was estimated by the shifts of the absorption bands of the amide carbonyl and N-H groups in the infrared spectra. From the results of the copolymerization between AAm and St, the greater the shift in the N-H absorption, the higher the amount of AAm found in the copolymer.     

Electrochemical Analysis of Acrylamide Using Screen‐Printed Carboxylated Single‐Walled Carbon Nanotube Electrodes

Acrylamide (AA) was electrochemically detected and quantified by means of its voltammetric response on carboxylic modified Single‐Walled Carbon Nanotube Screen Printed Electrodes (COOH‐SWCNT‐SPEs). The electroreduction signal of AA was proportional to AA concentration at low values (below 300 µM) and the observed sensitivity was explained in terms of AA adsorption on the COOH‐SWCNT‐SPEs that was demonstrated using the electrochemical response of [Fe(CN)₆]^3? and [Fe(CN)₆]^4? and Raman spectroscopy experiments. In order to test the suggested analytic approach (LOD of 0.03 µM, LOQ of 0.04 µM), detection and quantification of AA in fried potatoes was carried out using the proposed electrochemical method and HPLC. Both techniques showed similar contents of AA.     

Modified chitosan 4. Superabsorbent hydrogels from poly(acrylic acid-co-acrylamide) grafted chitosan with salt- and pH-responsiveness properties

Graft copolymerization of mixtures of acrylic acid (AA) and acrylamide (AAm) onto chitosan was carried out by using potassium persulfate (KPS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. The effect of reaction variables, such as MBA concentration and AA/AAm ratio on the water absorbency capacity have been investigated. The polymer structures were confirmed by FTIR spectroscopy. Water absorbencies were compared for the hydrogels before and after alkaline hydrolysis. In the non-hydrolyzed hydrogel, enhanced water absorbency was obtained with increasing AA in monomer feed. However, after saponification, the sample with high AAm ratio exhibited more water absorbency. These behaviors were discussed according to structural parameters. The swelling kinetics of the superabsorbing hydrogels was studied as well. The hydrogels exhibited ampholytic and reversible pH-responsiveness characteristics. The swelling variations were explained according to swelling theory based on the hydrogel chemical structure. The hydrogels exhibited salt-sensitivity and cation exchange properties. The pH-reversibility and on-off switching properties of the hydrogels make the intelligent polymers as good candidates for considering as potential carriers for bioactive agents, e.g. drugs.     

Hydrogen‐bonding Structures and Energetics of Acrylamide Isomers,Tautomers, and Dimers: An ab initio Study and Spectral Analysis

Hydrogen‐bonding patterns and energetic profiles of acrylamide isomers (syn‐ and skew‐), tautomers (amide and imidic acid forms) and 13 stable dimers have been studied using the second‐order Møller–Plesset perturbation theory with basis sets up to aug‐cc‐pVTZ. Syn‐acrylamide is the most stable monomer with a reaction barrier of 4.15 kcal/mol for the syn–skew isomerization reaction. The direct amide–imidic acid tautomerization reaction is separated by too high a barrier to surpass. The most stable dimer corresponds to the planar double‐hydrogen‐bonded configuration, indicating its crucial role in determining the stability of the formed complex. Moreover, hydrogen bonds have significant effects on the infrared spectral features, which can be consistently explained solely based on the acrylamide dimeric structures and energetics without monomeric and dimeric tautomer forms. The results are useful for studying the stability of the acrylamide clusters in condensed‐phase samples such as those in food chemistry studies.