Functional monomers and polymers. XCIV. Photochemical reactions on the synthetic polymers containing thymine bases in the presence of adenine derivatives

Photodimerization reactions of polyacrylate and polymethacrylate derivatives and the dimer model compound containing thymine bases were studied in the presence of adenine derivatives in dimethyl sulfoxide; N,N-dimethylformamide; and dimethyl sulfoxide–ethylene glycol solutions. The photodimerization of thymine bases both in the polymers and in the dimer model compound was found to be quenched by the addition of adenine derivatives. Base-base interaction in the ground state was also studied by ultraviolet (UV) spectroscopy in the three solvents. The quenching of the photodimerizationof thymine bases in the presence of adenine derivatives was discussed in terms of the specific interaction between adenine and thymine bases both in ground and excited states.     

Functional monomers and polymers. CXVII. Photochemical reactions on oligo- and polyethyleneimines containing pendant thymine bases: Effect of the spacer

The photodimerization reaction of thymine bases incorporated in the modified oligo- and polyethyleneimines, in which α-alanine or ß-alanine unit was inserted between the main chain and the pendant thymine bases, was studied both in aqueous and in dimethyl sulfoxide solutions. It was found that the quantum yields for the photodimerization for the oligomers were closely related to the intramolecular interaction in the ground state, while those of the copolymers were not related to the ground state interaction. It was suggested that the singlet energy migration was present in the case of the polyethyleneimine derivatives. This result is discussed in terms of the effects of the nearest-neighboring thymine units, the structure of the side chain, and the singlet energy migration, particularly for the copolymers.     

Functional monomers and polymers. XCV. Photochemical reactions on synthetic polymers having pendant thymine bases in polymethyl methacrylate film

The photodimerization reaction of synthetic polymers which contain thymine bases was studied in polymethyl methacrylate film. The quantum efficiency for the photodimerization of the thymine bases of polyacrylate and polymethacrylate, fixed in the polymethyl methacrylate film was measured. The value of the film was higher than those measured in solution.     

Functional monomers and polymers. CVIII. Photodimerization of pendant thymine bases in thymine containing poly-lysine derivatives

The photodimerization reaction of pendant thymine bases in thymine-containing poly-lysine derivatives was studied over a wide range in aqueous solution. It was found that the quantum yield of the photodimerization of pendant thymine bases is affected mainly by the conformation of the polymers in solution. The differences in photoreaction behavior were discussed for poly-D -, poly-L -, and poly-DL -lysine derivatives.     

Functional monomers and polymers. XCIII. Photochemical reactions on the acrylic and methacrylic copolymers containing thymine bases

Photodimerization of Polyacrylic and polymethacrylic derivatives with different pendant thymine unit content was studied in dimethylformamide solution. The quantum efficiency of thymine base for the photodimerization increased with increasing thymine content in the copolymers. The quenching study, which used isoprene as the quencher, revealed that the photodimerization resulted from excited singlet state increases with increasing thymine content. The photochemical results were discussed in terms of self-association of thymine bases in the polymer chain.     

Functional monomers and polymers. CXIII. Photoinduced conformational change of thymine containing poly-lysine derivatives

The photodimerization reaction between thymine bases in thymine-grafted poly-D - and poly-L -lysine derivatives was studied in an alkaline, aqueous, buffered solution. It was found that the helix content of the polymers changes by photodimerization. The result was discussed in terms of conversion, the rate of photodimerization, and the helix content of the polymers.     

Functional monomers and polymers. XCVI. Photochemical reactions on oligo- and polyethyleneimines which contain pendant thymine bases

The photodimerization reaction of oligo- and polyethyleneimine derivatives which contain pendant thymine bases in various amounts was studied in aqueous solution in a wide pH range and in N, N-dimethylformamide solution. The photodimerization reaction of these derivatives in poly(methyl methacrylate) was also studied. It was found that its quantum efficiency tended to increase as thymine units were added to the oligomers and copolymers. This result is discussed in terms of the effect of the nearest neighboring thymine units and singlet energy migration, particularly in the polymers.     

Functional monomers and polymers. XXXXVII. Complex formation of stereoregular methacryloyl-type polymers containing nucleic acid bases

The complex formation between a poly(N-β-methacryloyloxyethyl) derivative of adenine with one of thymine or uracil was studied in dimethyl sulfoxide and ethylene glycol mixture by ultraviolet (UV) spectroscopy. For the polymer pairs containing complementary nucleic acid bases both hypochromicity and hyperchromicity were found. Stereoregularity of the polymers, as well as the conditions for measurement of, for example, solvent, temperature, and time, affected the complex formation. Both inter- and intramolecular interaction of polymers in solution were discussed in some detail.     

Functional monomers and polymers. LXI. Photochemical reactions on the synthetic polymers containing thymine bases

Photodimerization of N-2-isobutyloxyethyl thymine (T-M), bis[2-(5-methyl-1-primidinyl)-ethyl] glutarate (T-T), poly(N-2-methacryloyloxyethyl thymine) (polyMAOT), and poly(N-2-acryloyloxyethyl thymine) (poly AOT) was studied in dimethylformamide solution. The rate of intramolecular photodimerization of polyMAOT and polyAOT was 5.7 and 7.2 times faster, respectively, than that of T-T. In T-M, however, intermolecular photodimerization did not occur under the reaction condition used. Quenching studies with isoprene suggest that the photodimerization of T-T occurs predominantly in an excited triplet state, whereas that of polyMAOT and polyAOT occur in singlet and triplet states. It was concluded that the photodimers of T-T, polyMAOT, and polyAOT are two syn-fused cyclobutane-type dimers (cis-syn and trans-syn). Quantum efficiencies of thymine base disappearance were determined by ultraviolet (UV) analysis to be 0.0012 for T-T, 0.0084 for polyMAOT, and 0.010 for polyAOT.     

Photodimerization of Thymine-Containing Polymers: Applicability to Reversible Photoresists

The intramolecular photodimerization of thymine bases present on the side chain of a variety of synthetic oligomers and polymers was studied in detail in various organic solvents, and particularly in the case of thymine-containing polylysines, over a wide range of pH. Effects of solvents, presence of the complementary base, and spacers on the photoreaction were examined, and the conformational changes of the polymers were discussed in relation to their functionalities. Intermolecular photodimerization was further studied, and its applicability to photoresists was shown.     

Functional monomers and polymers. CXXI. Methylation and interaction studies on adenine containing polymethacrylate derivatives

Studies of the methylation of polymethacrylate derivatives with adenine bases were made in comparison to those with uracil bases. The polymethacrylate derivatives with adenine bases were methylated by using methyl iodide in dimethyl sulfoxide solution to produce polymers that contained N¹-methyladenine and N¹, N⁶-dimethyladenine units. The products were identified by spectroscopic data and by preparing their model compounds. The methylated polymers obtained were further applied in a study of polymer complex formation with uracil-base polymers.     

Functional monomers and polymers. CXIX.. Synthesis and photochemical reaction of polymethacrylate derivative containing 6-cyanouracil

A polymethacrylate derivative containing 6-cyanouracil was prepared, and its photochemical reaction was studied. The 6-cyanouracil derivative was found to show high reactivity for the photochemiccal reaction. The photochemical-reaction product was identified as a cyclobutanetype photodimer, and the photodimer was formed in high yield even from the monomeric compound of 6-cyanouracil under UV irradiation in low concentration. The quantum yield of the photodimerization of the 6-cyanouracil derivative was greater than that of the thymine derivative. The photodimerization of the 6-cyanouracil derivative could not be quenched by usual triplet quenchers, but was found to be quenched by the polymeric derivative of adenine, suggesting a specific interaction.     

Functional monomers and polymers. CLIV. Application of nucleic acid base containing polymers to high performance liquid chromatography

Poly-L -lysine (PLL) derivatives containing pendant nucleic acid base, such as thymine or adenine, were bonded successfully to 3-aminopropylsilanized silica (APS-silica) and silica gel. These resins were found to be useful as the column of high performance liquid chromatography (HPLC) for the selective separation of oligoethyleneimine derivatives having pendant thymine or adenine bases.     

Thymine‐based,water‐soluble phototerpolymers: Their preparation and synthesis

Terpolymers of vinylbenzylthymine, vinylbenzyltriethylammonium chloride, and N‐butyl‐N,N‐dimethyl‐(4‐vinylbenzyl)ammonium chloride with different monomer ratios have been prepared, and the effect of the monomer ratios on the properties of the terpolymers has been investigated. These polymers are water‐soluble and, when irradiated with low levels of UV light, undergo a 2π+2π photodimerization reaction of thymine. This photodimerization significantly reduces the water solubility, immobilizing the polymer to the substrate, and shows potential for water‐soluble photoresists. Thermogravimetric analysis has revealed that the terpolymers have two degradation stages corresponding to the quaternary ammonium pendant groups and to the thymine. An evaluation of the contact‐angle measurements has shown that the surface properties and hydrophobicity can be controlled by the variation of the monomer ratios. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1296–1303, 2007     

Functional monomers and polymers. XCVII. Synthesis of oligomer models of polyethyleneimine derivatives containing pendant thymine bases

A series of oligomer models of polyethyleneimine derivatives having pendant thymine bases were prepared by the reaction of carboxyethyl derivatives of thymine with oligomer amines using an activated-ester method. It was found that the hypochromicity values obtained from UV spectra and pKa values obtained from spectrophotometric titrations depend on the chain length of the oligomers and the thymine content of the polymers.     

Functional monomers and polymers. CIV. Synthesis and properties of oligomer models of polyethyleneimine derivatives with spacer-separated nucleic acid bases

A series of polyethyleneimine derivatives and their oligomer models with pendant thymine or adenine bases separated by β-alanyl groups as spacers were prepared by an activated ester method. To elucidate the nature of intramolecular interaction of thymine and adenine bases ultraviolet (UV) spectrophotometric studies were undertaken for the series of compounds and the results were compared with those obtained for the corresponding oligomers without spacers. In the thymine derivatives, the nature of the intramolecular interaction resembled that of the corresponding compounds without β-alanyl units, although larger hypochromicities were found in the series with β-alanyl units. In the adenine derivatives, contrary to the corresponding thymine systems, UV hypochromicities of the compounds decreased by incorporation of the spacer group into side chains. It became evident that the intramolecular interaction of adenine bases was due to stacking neutral species, hydrogen bonding, and residual hypochromicity for the protonated species.     

Water soluble nucleic acid analogs: Preparation and properties

In order to prepare water soluble natural and synthetic polymers, which contain nucleic acid base units as the functional side groups, a different sort of polymers, such as poly(ethyleneimine), poly(amino acids) and so on were used as the base materials. The properties of the polymers derived, in particular the specific interaction between nucleic acid base containing complementary polymers was studied in detail. Introduction of the base units onto hyaluronic acid was also carried out. Applicabilities of these polymers obtained, for example as the controlled release system by using reversible photodimerization reaction of thymine bases were also shown.     

Solution properties of dendronized poly(hydroxy ethyl methacrylate) polymers

Four generations of dendronized polymers with a methacrylate backbone and hydroxy‐functionalized aliphatic polyester dendrons based on 2,2‐bis(methylol)propionic acid were studied in solutions by rheological measurements, dynamic light scattering, turbidimetry, and ¹H NMR self‐diffusion measurements to reveal the effect of increasing hydrophilicity and molecular size on their solution properties. The studied polymers were interesting new amphiphiles with a hydrophobic main chain and a hydrophilic shell. Evidence of aggregation upon the heating of the first‐generation polymer in an aqueous solution was obtained by dynamic light scattering and turbidimetry, reflecting the effect of the hydrophobic polymer backbone, whereas the higher generation polymers did not show aggregation upon heating. Although the dimensions of the polymers were observed to increase with increasing generation, all the polymers exhibited low viscosities and Newtonian flow behavior in both aqueous and dimethyl sulfoxide solutions. The relative viscosities of the polymers in water and dimethyl sulfoxide showed that the conformation of the polymers was somewhat more open in dimethyl sulfoxide, and this led to higher viscosities than those in water, in agreement with the ¹H NMR diffusion measurements, by which the dimensions were found to be larger for the polymers dissolved in dimethyl sulfoxide. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3674–3683, 2006     

Functional monomers and polymers 159 synthesis and photochemical reactions of polymers containing thymine photodimer units in the main chain

Polyamides containing thymine photodimer units in the main chain were synthesized, and their photolysis by ultraviolet irradiation below 260 nm were studied in film state. Photodimers of thymine derivatives were obtained by photochemical reaction of the carboxylic acid derivatives of thymine in aqueous solution irradiated above 270 nm. An attempt was made to resolve the isomers of the photodimers, and the two kinds of cis isomers [cis–syn(head to head), and cis–anti(head to tail)] were isolated successfully. The polyamides were prepared by condensation of the photodimers with diamine using an activated ester method. The photodissociation of the thymine photodimer in the polymer main chain caused the breakage of the polymer chains, leading to the production of oligomers and dimer compounds containing thymine bases at the ends of the molecule. The dissociation rate of the polymer did not depend on the kind of the thymine photodimer which was in the main chain of the polymer.     

Light-induced aggregation of colloidal gold nanoparticles capped by thymine derivatives

The colloid stability of thymine-coated gold nanoparticles under light irradiation as a function of particle size, surface charge, and exposure time was investigated in alkaline, aqueous solutions as well as in a 0.5 vol % of DMF in H(2)O mixture. With increasing exposure to light irradiation at 280 nm, more and more particles coagulated. Light-induced aggregation of colloidal gold nanoparticles was attributed to reorientation of thymine terminal groups tethered on gold particle surfaces. A smaller particle size and negatively charged surface reduced the rate of photodimerization or even inhibited the photoreaction. UV-vis and FTIR spectroscopy confirmed the photodimerization of terminal thymine molecules under 280 nm light irradiation. The reaction kinetics of thymine photodimerization appears to be a combination of first-order reactions, each having different rates, reflecting the inhomogeneity and high curvature of the gold nanoparticle surfaces.