Irradiated Poly Research Articles

Determination of UV-laser induced surface structures by atomic force microscopy

The changes in surface topography due to UV-laser treatment are of high significance for the determination of material destruction thresholds and for surface reconstruction. A combined arrangement of an UV-laser and an atomic force microscope (AFM) allows for the first time a highly sensitive surface characterisation of the very same area of the irradiated sample between different laser pulses. Irradiation of poly(ethylene terephthalate) (PET) with pulsed UV-laser light of 248 nm, modifies the smooth surface of the polymer into a well-oriented structured surface. The evolution of such structures was studied. A change in surface topography was found in relation to fluence and number of pulses applied. A statistical interpretation of AFM images gives some indications to the mechanism of material processing.

Reductions in rate of yellowing following irradiation of poly[N(n‐butoxymethyl) methacrylamide]‐grafted silk fibers

AbstractThe physical properties, including changes in the yellowness index, following UV irradiation of Bombyx mori silk fibers loaded with poly[N(n‐butoxymethyl) methacrylamide], poly(BMA), are examined in relation to the amount of held polymer. The percentage weight gain by the silk fibers observed after 45 min at 80°C increased with increasing initial amounts of BMA monomer in the reaction system. Differential scanning calorimetry (DSC) observations suggest that the thermal decomposition behavior of the heated silk fiber was little affected, with but an apparent small shift of the endothermic decomposition temperature range to higher temperatures. The tensile properties of the treated silk fibers remained effectively unchanged, independent of the polymer weight gains. There was, however, a marked effect of the poly(BMA) weight gains onto silk in maintaining the whiteness and reducing the rate of yellowing following irradiation of treated habutae silk fabrics. These observations suggest that the rate of photoyellowing of silk fabrics can be retarded by the presence of the poly(BMA) in the fabric. © 1993 John Wiley & Sons, Inc.

Surface characterization of laser‐treated poly(ethylene terephthalate) by optical profilometry and scanning tunneling microscopy

AbstractCharacteristic changes in the surface topography due to UV laser treatment are of high significance for the determination of material destruction thresholds and surface structure development. E.g. irradiation of poly(ethylene terephthalate) (PET) film with pulsed UV laser light of 248 nm modifies the smoth surface of the polymer into a well oriented structured surface. The development of these structures were studied with scanning tunneling microscopy (STM) and high resolution optical profilometry. Three dimensional data of the surface were taken from the samples after each laser pulse. A change of topographic data was found in relation to fluence and number of pulses applied. © 1993 John Wilcy & Sons, Inc.

Study of diffusion of a fluorinated hydrocarbon in ion beam irradiated poly(styrene) by nuclear resonance analysis

The diffusion of a fluorinated hydrocarbon into 30 keV-H+ irradiated glassy poly(styrene) (PS) was studied by using nuclear resonance reaction analysis. The diffraction coefficient and front velocity for diffusing a particular fluorinated hydrocarbon, 3, 5-bis (trifluoromethyl) aniline (TFMA) in PS (MW=400 000) are dramatically decreased on irradiation with 5×1013–1×1014 atoms/cm2 at 22.5 °C. These ion beam irradiation effects are similar to temperature effects on diffusion. A possible application of the observed effect is the control of diffusion of a vapor into cross-linked polymer glasses by means of ion beam implantation techniques. It is our belief that this is the first report of this phenomena due to the effects of ion beam irradiation.

Infrared study of the thermal behavior of ?-irradiated poly-(vinyl alcohol)

Infrared spectroscopy was applied for the investigation of the combined effects of γ-irradiation and heat on polyvinyl alcohol (PVA). The samples were exposed in an atmosphere of air at room temperature to doses ranging form 0.5 to 15 M rads. The obtained results revealed that exposure to γ-irradiation produces no considerable changes in the IR spectra of PVA apart from very slight changes in the intensities of the absorption bands. The crystallinity of the irradiated samples was determined by following the induced changes in the absorbances of the crystalline bands. The IR spectra of PVA samples heated at 180°C exhibited two absorption bands at 1580 and 1710 cm−1 due to carbonyl groups. Alken double bonds and possibly also carboxyl groups. IR spectroscopy was also used for the examination of the effect of time of heating in air or in vacuum and also the effect of quenching of the degree of crystallinity of γ-irradiated PVA. Careful examination of the IR spectra led to the conclusion that the temperature induced changes depend on time of heating, rate of cooling and γ-dosage used. The highest crystallinity was obtained by heating in vacuum at 140°C and quenching at −40°C.

Charge-mosaic membrane from gamma-irradiated poly (styrene—butadiene—4-vinylpyridine) triblock copolymer. II. Prelimineary dialysis test

In the present paper the variations of the physicochemical properties of a charge-mosaic membrane with the pH of solution were investigated. Charge-mosaic membranes with a well-defined domain structure and strong mechanical and chemical stability were prepared from irradiated poly (styrene—butadiene—4-vinylpyridine) triblock copolymer. The membrane conductivity (or salt flux) of the charge-mosaic membrane increases with pH in the pH range 2–6) and reaches a maximum at pH 6. On further increase of the pH (in the range 6–10), the membrane conductivity (or salt flux) decreases again. However, the amount of non-electrolyte (protein or sucrose) flux through membrane could not be detected over the whole pH range studied. The remarkable effect of pH on the membrane properties can be illustrated by an analysis of the microstructure of the charge-mosaic membrane and by the amount of the hydrogen and hydroxyl ions formed at the different pHs. Dialysis coefficients determined from a mixed solution of 0.1 N KCl and 0.1 g/100 ml protein (or 0.1 N KCl and 0.1 N sucrose) were 1.07 × 10 −8 mol/cm 2-sec and 1.10 × 10 −8 mol/cm 2-sec respectively. The high salt permeability seems to originate from the well-defined domain structure in the precursor film (cast from a mixed solution of n-butyralydehyde and chloroform) and indicates that the transport of salt through these charge-mosaic membranes occurs by a mechanism typical for such a membrane.

Intramolecular vs intermolecular formation of bityrosine upon photoreaction of poly(l-tyrosine) in dilute aqueous solution

The molecular weight dependence of the rate of the formation of bityrosine upon irradiation of poly(L-tyrosine) at 300 nm has been investigated in dilute aqueous solution, pH 12. The samples studied were the monodisperse monomer, dimer, trimer, and hexamer, as well as two polydisperse polymers with average degrees of polymerization of ∼ 102 and ∼ 103. The reaction is predominantly intermolecular in the monodisperse oligomers, but it is predominantly intramolecular in the two polymers. The intramolecular reaction in the polymers involves phenolic rings on monomers i and i+j, with j>5. The steric restraints imposed by the backbone of the chain make it unlikely that two rings will approach one another with the appropriate geometry for reaction if j<5.

Characterization of highly irradiated poly(vinyl chloride)

Irradiated poly(vinyl chloride) has been characterized by various techniques. The very high doses (up to 20 Mgy) produce dramatic changes in the material. Chemical changes were studied by TGA analysis. Surface morphology and microstructure were determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). PVC irradiated at the highest dose, 20 MGy, shows a structure consisting mainly of carbon which, in some cases, is crystalline. This carbon-rich material also shows a particular affinity for the adsorption and desorption (after electron bombardment) of ambient gases, as is clearly shown in electron stimulated desorption (EDS) experiments performed in this study.

Effect of methanol on optical property of irradiated poly(methyl methacrylate)

AbstractThe effect of methanol on optical property of irradiated poly(methyl methacrylate) (PMMA) has been investigated. The gamma irradiation enhances the methanol transport in PMMA. The activation energies of diffusivity for case I and velocity for case II decreases with increasing gamma ray dose. For the same wavelength, in the range 350–800 nm, the transmittance decreases with increasig gamma ray dose. The equation of transmittance I with gamma ray dose ϕ at the wavelength 405 nm is I = I0 exp(−0.06ϕ1/2), where I0 is the transmittance of virgin PMMA. When the irradiated PMMA is immersed into methanol bath, the yellow color fades out gradually. The recovery of transmittance increases with methanol content in irradiated PMMA. The boundary to separate the outer region (solvent affected zone) from the inner region (no solvent‐affected zone) is also studied. The rate of boundary movement increases with gamma ray dose.

An ESR study of free radicals formed in irradiated poly(alpha-methyl styrene) by gamma-radiation

The radiolysis of poly(α-methyl styrene) with γ-radiation has been studied at 77 and 300 K by ESR spectroscopy. The radical intermediates formed at these temperatures have been identified by utilization of the techniques of photobleaching, thermal annealing and simulation. The radical yields were found to be 0.105±0.005 at 77 K and 0.05±0.003 at 298 K.

Irradiation of poly- d,l-lactide

Compression-moulded samples of poly- d,l-lactide have been γ-irradiated in air to give received doses up to 10 Mrad. Molecular weight and mechanical property changes have been established and are consistent with a random scission process. Substantial embrittlement occurs at the higher dose levels. The radiochemical yield for scission G(s) has been calculated to be 2·9 over the dose range examined. The properties of irradiated materials have been monitored over a 504-day period and show no evidence of post-irradiation aging. Moisture uptake has been measured by immersion in pH 7·4 buffer at 37°C and indicates that the irradiated material absorbs water at a slightly slower rate than the unirradiated material. The primary effect of irradiation on hydrolytic degradation is associated with the initial reduction of molecular weight and there are no subsequent changes in degradation mechanism.

Surface reconstruction of UV-laser irradiated poly(ethylene terephthalate) by atomic force microscopy

Atomic force microscopy (AFM) is utilized for the evaluation of change in the surface topography of highly absorbing poly(ethylene terephthalate) (PET) films after UV-laser treatment with 248 nm. Three-dimensional data of the surface microstructure were taken from samples. Particularly low fluence treatment with a few laser pulses was studied. A change in surface topography was found in relation to the number of pulsers applied.

Optical absorption in gamma irradiated poly(vinyl alcohol)‐CoCl2 composites

AbstractOptical absorption measurements were performed on cast thin films of poly(vinyl alcohol) and its composites with cobalt chloride before and after gamma irradiation. Identification of the structure and assignments of energy bands have been derived in terms of ligand field theory. A mechanism based on the equilibrium between six‐coordinated and four‐coordinated symmetry is proposed to account for the obtained spectra. The symmetry is found to be altered with both cobalt concentration and gamma irradiation dose.

On the formation of 1,4,8,11-tetraoxa-12,12,13,13-tetrafluoro-6-trifluoromethyl-dispiro[4.1.4.2]-Tridecan

Some of us have studied the manufacturing of perfluoroalkenes by irradiation of poly(tetrafluoroethylene) using accelerated electrons [1,2]. These perfluoroalkenes are obtained, as a mixture of homologous and isomers together with the corresponding homologous of perfluoroalkanes. Such mixtures are suitable to synthesize fluorosurfactants and other products for industrial processes [3]. Nevertheless, only mixed products were obtained at all reactions studied. Therefore, we were surprised to got a crystalline product as a well-defined substance in one case. The title compound ▪ has been fully characterized. Its existence is an evidence for cyclic products in above mixtures. The origin of I and its characterization will be reported.

Novel synthesis of poly(benzoin) and poly(benzil). Characterization and application as photosensitizer materials

AbstractNew photoactive polymers containing benzoin or benzil groups have been prepared by condensation of terephthalaldehyde. The influence of the alkali metal ions and solvents used upon the progress of polycondensation and yield of poly(benzoin)Systematic name: Poly(1,4‐phenylene‐1‐hydroxy‐2‐oxoethylene). were studied. Oxidation of this polymer by nitric acid or ammonium nitrate in acetic acid afforded the corresponding poly(benzil)Systematic name: Poly(1,4‐phenylene‐1,2‐dioxoethylene). in quantitative yield. The resulting polymers were confirmed by elemental analysis, IR, 1H NMR and UV/visible spectral data, and characterized using viscometry, DTA measurements, thermogravimetric and X‐ray analysis. The photosensitizing property of the prepared polymers was detected by fluorescence. It was found that irradiation of poly(benzoin) in DMSO solution at 285 nm causes yellow fluorescence whereas poly(benzil) does not display fluorescence at the same excitation wavelength. Moreover, the use of poly(benzil) as photosensitizer material in the photochemical cleavage of thiourea and its derivatives was also studied.

Stability of DNA thymine hydrates

Pyrimidine hydrates are products of ultraviolet irradiation of DNA. We have already demonstrated the formation of both cis-thymine hydrate and trans-thymine hydrate (6-hydroxy-5,6-dihydrothymine) in irradiated poly(dA-dT):poly(dA-dT). These are released from DNA as free bases by bacterial or human glycosylases. Thymine hydrate stabilities were studied in irradiated DNA substrates using purified E. coli endonuclease III as a reagent for their removal. After irradiation, substrate poly(dA-dT):poly(dA-dT), radiolabeled in thymine, was incubated at 50, 60, 70 or 80 degrees C, cooled, and then reacted with the enzyme under standard conditions. Thymine hydrates were assayed by enzymic release of labeled material into the ethanol-soluble fraction. Their identities were confirmed by high performance liquid chromatography. The decay of thymine hydrates in heated DNA followed first-order kinetics with a k = 2.8 x 10(-5)/sec at 80 degrees C. These hydrates were also detected in lesser quantities in the unirradiated, control substrate. Extrapolation from an Arrhenius plot yields an estimated half-life of 33.3 hours at 37 degrees C for DNA thymine hydrates. Such stability, together with their formation in unirradiated DNA, suggest thymine hydrates to be formed under physiological conditions and to be sufficiently stable in DNA to be potentially genotoxic. This necessitates their constant removal from DNA by the excision-repair system.

Radiophotoluminescence of irradiated poly(methyl methacrylate) doped with some charge transfer complexes

The radiophotoluminescence (RPL) of irradiated and non-irradiated thin films of poly(methyl methacrylate) (PMMA) doped with anthracene (Anth), as a donor, and tetracyanoquinodimethane (TCNQ), as an acceptor, has been investigated. The RPL glow spectrum was recorded to study the characteristic emission bands from the point of view of glow peak position and intensity and hence the prospective relative sensitivities. RPL signal fading after one month of storage in the dark at room temperature after gamma irradiation was also studied. PMMA doped with a donor to acceptor ratio of 6:4 has been proved to be the most sensitive with less fading as regards gamma detection. On the other hand 2 Anth:8 TCNQ was found to be the best dopant concentration ratio for thermal neutron detection.

Dielectric Properties of γ-Ray Irradiated Poly(vinylidene Fluoride)

The dielectric properties of γ-ray irradiated poly(vinylidene fluoride) (PVDF) were studied at temperatures from 213 to 423 K. The relaxation intensity, Δε, of both the β and α relaxations decreased with increasing irradiation dosages. The decrease of Δε in the β and α relaxations was ascribed to an increase in crosslinking in the amorphous regions and at lamellar surfaces, respectively. When irradiated PVDF was crystallized from the melt under uniaxial compression, Δε of the β relaxation increased with increasing compression ratio, while that of the α relaxation decreased. The increase of Δε in the β relaxation is explained by the increase of molecular chains oriented parallel to the film plane. The decrease of Δε in the α relaxation is due to conversion of form II crystal into form I.

Crystallization in highly irradiated poly(vinyl chloride)

Poly (vinyl chloride) is one of the most widely used materials in today’s society, and the study of its properties is relevant to many fields. In the present case, we investigate changes that occured in this material when it was exposed to high doses of gamma rays. Previous studies using electron beam irradiation indicated the possibilities of using this material as a “getter” due to its ability to capture gases like CO2 and CO. The present work deales with preliminary results on the structural characteristics of a carbon rich material obtained using ionizing radiation.Radiation treatment was done in several steps, a) irradiation of 1000 Mrad (at dose rate of 0.95 Mrad/hr) in a Gamma Beam Type 651-PT ( Co) source. b) the sample is then extracted with tetrahydrofuran (THF) in order to separate the homopolymer from the gel that was formed during irradiation. c) the gel fraction (crosslinked polymer) was filtered, dried and weighted, and exposed again for 200 Mrad more

Computer‐simulated ESR spectra of irradiated poly(olefin oxides)—effect of glass transition temperature on the ESR spectra

AbstractInvestigations on the effects of γ irradiation on poly(methylene oxide) (POM) and poly(ethylene oxide) (PEO) have been made employing electron spin resonance (ESR) spectroscopy. The ESR sextet and doublet spectra, recorded for POM and PEO, respectively, on irradition in air at room temperature are broadened as the temperature is lowered and show a reversible change in line shape with temperature. The spectra are analyzed by computer simulation, employing Lorentzian line‐shape functions and the least‐squares method of total curve fitting. The component spectra are evaluated and are assigned. Superposition of the component quartet, triplet, and doublet spectra, corresponding to the radicals ĊH3, ĊH2O , and OĊHO , respectively, together with a singlet due to the radicals ȮCH2 is considered to be the best fit to the observed spectrum for POM. The doublet spectrum recorded for PEO has been assigned to the radicals ĊHO . The reversible broadening of the spectra has been associated with the mechanism of molecular motions around the glass transition temperatures of these polymers.