Side Double Bond Research Articles

A novel CO2 based UV-induced peelable adhesive for wafer dicing

Poly (propylene carbonate) diol with double-bonds on the side chains (PPCAGE) was synthesized form CO2, propylene oxide (PO), polyether diol (PPG) and allyl glycidyl ether (AGE). Then, three kinds of CO2 based polyurethane oligomers (PPCAGE-PU) (PPCAGE-PUA, PPCAGE-PUB and PPCAGE-IPDI, respectively) with different contents of double bond were prepared through the reaction of PPCAGE, isophorone diisocyanate (IPDI) and hydroxyethyl acrylate (HEA). The content of -NCO was adjusted by varying the ratio of -NCO terminated prepolymer and HEA. Acrylate copolymer with side double bonds and hydroxyl groups (GMA-PSA) was synthesized by the ring-opening reaction of glycidyl methacrylate (GMA) and acrylate copolymer (PSA) containing -COOH and -OH. CO2 based UV-induced peelable adhesive was prepared by mixing PPCAGE-PU, GMA-PSA, active diluent and photoinitiator. The structure of PPCAGE was confirmed by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (1H NMR). The reaction of PPCAGE-PUB and GMA-PSA was monitored by FT-IR, companied by the titration of -NCO and epoxide. The molecular weight of PSA and GMA-PSA was determined by gel permeation chromatography (GPC). The surface morphology of the adhesive was observed by scanning electron microscopy (SEM). The viscoelasticity of adhesive was measured by real-time rheology. The 180° peel strength, micro-surface morphology, gel content, unsaturation conversion and glass transition temperature of UV-induced peelable adhesive were characterized. The results showed that the peel strength of adhesive was 17.82 N/25 mm before UV curing. After UV curing, the surface morphology changed from smooth to rough, the peel strength decreased to 0.08 N/25 mm and the modulus of the PSA increased due to the cross-linking. DSC results showed that the glass transition temperature increased after UV curing.

(Invited) Crosslinked High Temperature Polymer Electrolyte Membranes

High temperature polymer electrolyte membranes containing basic units that are able to interact with strong protic acids providing ionically conductive composite membrane have shown respectable performance and long operational stability. Further increase of the operation temperature and even an increase on the obtained conductivity values would facilitate the construction of efficient systems providing both electricity and heat, increasing thus the total efficiency. Initial attempts to stabilize the HTPEM electrolyte membranes through covalent crosslinking have proven that the operation temperature can be shifted up to 220oC 1,2. Different crosslinking methodologies have been tested to stabilize either PBI or aromatic polyethers bearing pyridine units3,4. In the present work we focused on the optimization of the crosslinking methodology using side double bonds and we also develop new crosslinking methodologies leading to wholly aromatic crosslinked structures. Different type of crosslinkers have been used, controlling thus the acid doping ability of the final membranes while the use of dopable crosslinkers that enable the high acid uptake and retention. Moreover, depending on the chemical structure of the crosslinked membranes, a significant increase of the conductivity values of the final acid doped composite membranes was obtained. High temperature operation as the one achieved here enables the use of liquid feed like methanol in a compact methanol reformer-high temperature PEM fuel Cell setup that is under construction and testing5.

Covalent cross-linking in phosphoric acid of pyridine based aromatic polyethers bearing side double bonds for use in high temperature polymer electrolyte membrane fuelcells

Cross-linkable aromatic polyethers combining main and side chain pyridine units as well as side double bonds were successfully synthesized and characterized. Aiming at the use of these materials as electrolytes at high temperature fuel cells, these polymers were subjected to covalent cross-linking in order to improve their mechanical properties and their stability in the doped state. The cross-linking was obtained via cationic polymerization of the double bonds, during the impregnation of the produced membranes in phosphoric acid. The cross-linking was confirmed by the increased glass transition temperatures, the improved thermal stability and the insolubility of the cross-linked membranes compared to their undoped non cross-linked counterparts. Selected cross-linked membranes were used for membrane electrode assembly (MEA) preparation and tested in a single cell at temperatures between 180 and 220°C. Long-term durability tests were also performed at 180°C and at a current density of 0.2A/cm2. The experiment showed a stable operation without degradation for 1000h. The promising performance and the durability of the tested materials in combination with the simple and convenient technique which used to produce cross-linked membranes, demonstrates the feasibility of this type of electrolytes to be used in high temperature PEM fuel cell applications.

Application of silver ion in the separation of macrolide antibiotic components by high-speed counter-current chromatography

Three macrolide antibiotic components – ascomycin, tacrolimus and dihydrotacrolimus – were separated and purified by silver ion high-speed counter-current chromatography (HSCCC). The solvent system consisted of n-hexane– tert-butyl methyl ether–methanol–water (1:3:6:5, v/v) and silver nitrate (0.10 mol/l). The silver ion acted as a π-complexing agent with tacrolimus because of its extra side double bond compared with ascomycin and dihydrotacrolimus. This complexation modified the partition coefficient values and the separation factors of the three components. As a result, ascomycin, tacrolimus and dihydrotacrolimus were purified from 150 mg extracted crude sample with purities of 97.6%, 98.7% and 96.5%, respectively, and yields over 80% (including their tautomers). These results cannot be achieved with the same solvent system but without the addition of silver ion.

Photoreaction of Skin‐sensitizing Trimethyl Psoralen with Lipid Membrane Models

The concerted photoreaction between trimethyl psoralen (TMP) and isomeric model compounds of oleic acid methyl ester (OAME) and eadilic acid methyl ester (EAME) are explored using density functional theory. The S(1) surfaces all reveal large barriers (25-31 kcal/mol) to reach the decay channels, whereas the S(2) surfaces differ considerably between the furan and pyrone side adducts. For the pyrone side adducts, a small barrier to reach the intersection between the S(1) and S(2) states is found, followed by a small second barrier on the S(1) surface to the low-lying decay channel. For the furan-side adducts, no such intersection between S(1) and S(2) is seen, which thus prevents these products from being formed in high yields. The photoinduced cycloaddition is more favorable between OAME and the pyrone side double bond of TMP than for any of the other systems, which agrees with the experimental findings that this is formed in the highest yield. The computed UV absorption spectra of TMP and the TMP(pyrone)-OAME cycloadduct agree well with the experimental spectra.

2,6‐Di‐tert‐butyl‐4‐(3,3‐diarylpropadienylidene)‐2,5‐cyclohexadien‐1‐ones, the First Stable p‐Quinopropadienes

AbstractTreatment of 2,6‐di‐tert‐butyl‐4‐ethynylphenol with 2 equivalents of nBuLi, followed by addition of diaryl ketones, afforded the corresponding p‐quinopropadienes 2a−f upon appropriate dehydrative treatments. These compounds are fairly stable, orange to purple, crystalline substances, exhibiting intense absorptions at longer wavelengths. In particular, the bis(dimethylamino) derivative 2a absorbs across the whole of the visible spectrum and into the near infrared. Unlike the quinone methides 1, compounds 2 exhibited irreversible oxidation waves together with irreversible reduction waves on cyclic voltammetry. The very small E1sum value of 2a also indicates the highly amphoteric redox properties of 2a; however, both the anion and cation radicals of 2 are highly reactive. The molecular structures of 2a and 2e exhibit relatively small dihedral angles between two aromatic ring planes (2a for 47° and 2e for 52°), and each has a short central double bond and long side double bonds. The short central double bond (2a for 1.228 Å and 2e for 1.235 Å) indicates the importance of the resonance contribution of the dipolar structure with an acetylenic bond. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Dark and Photochemical Interactions of Dimethyltetrahydrobenzoangelicin with DNA

A study of dark interaction and photoreaction between 4,6-dimethyltetrahydrobenzoangelicin (THBA) and DNA is described. 4,6-Dimethyltetrahydrobenzoangelicin is a furocoumarin derivative in which 4' and 5' carbons are linked by a four-methylene bridge. In spite of the bulky aliphatic ring, THBA forms a complex with DNA in the dark and, on UVA irradiation, reacts with pyrimidine bases of DNA yielding monoadducts only involving its furan side double bond. Two main photoproducts form: they derive from a C4-cycloaddition to thymine and cytosine, respectively, and account for 56% and 39% of the total photoreaction yield. Both show cis-syn configuration. Two other isomers, one with thymine and one with cytosine, formed with so much lower yield (ca 3 and 1%, respectively) that their structure could not be assigned. Furthermore, in spite of its angular structure, THBA induces a small number of crosslinks in DNA.

Dark and Photochemical Interactions of Dimethyltetrahydrobenzoangelicin with DNA

A study of dark interaction and photoreaction between 4,6-dimethyltetrahydrobenzoangelicin (THBA) and DNA is described. 4,6-Dimethyltetrahydrobenzoangelicin is a furocoumarin derivative in which 4’and 5’carbons are linked by a four-methylene bridge. In spite of the bulky aliphatic ring, THBA forms a complex with DNA in the dark and, on UVA irradiation, reacts with pyrimidine bases of DNA yielding monoadducts only involving its furan side double bond. Two main photoproducts form: they derive from a C4-cycloaddition to thymine and cytosine, respectively, and account for 56% and 39% of the total photoreaction yield. Both show cis-syn configuration. Two other isomers, one with thymine and one with cytosine, formed with so much lower yield (ca 3 and 1%, respectively) that their structure could not be assigned. Furthermore, in spite of its angular structure, THBA induces a small number of crosslinks in DNA.