In 1982, the first reports of laser ablation of polymers were issued almost simultaneously by Y. Kawamura et al.1 and R. Srinivasan et al.2 Srinivasan went on to become a leader in the field of polymer ablation. Srinivasan probably also coined the terms laser ablation and ablative photodecomposition, now in common use. The onset of material removal by laser ablation characteristically occurs at a well-defined laser fluence (energy per unit area). As the fluence is raised above this threshold, the ablation rate increases. The threshold fluence (F0 or Fth) is material and laser wavelength dependent and can vary from tens of mJ cm-2 to more than 1 J cm-2. The discovery of laser ablation of polymers sparked research in this field in many groups around the world. Many aspects of polymer ablation, and laser processing in general, are reviewed by Bauerle.3 Today, commercial applications of polymer laser ablation include the preparation of viaholes in polyimide for multichip modules at IBM4 and the production of inkjet printer nozzles (also polyimide).5 Considerable progress has been made in understanding polymer ablation since the last series of reviews a decade ago.6-8 New developments in polymer ablation include the application of femtosecond laser pulses, vacuum ultraviolet lasers (VUV), and free electron lasers (FEL). Some of these techniques have a great potential for the development of new applications and research tools. Much of this progress is discussed in this and other articles appearing in this special issue of Chemical Reviews. Current research on polymer ablation may be divided into two areas: (i) Applications of laser ablation, novel materials, and techniques. (ii) Studies of ablation mechanisms (databased modeling). The first area will be discussed in detail in this article, while the mechanistic aspects, especially the theoretical part, are discussed in other articles in this special issue. Many experimental methods and experimental polymers have been designed with a view toward improving our understanding of ablation mechanisms. It is often impossible to completely separate experiments designed to illuminate ablation mech† Paul Scherrer Institut. ‡ Washington State University. 453 Chem. Rev. 2003, 103, 453−485

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Chemical and spectroscopic aspects of polymer ablation: Special features and novel directions

A Bragg grating in a single-mode polymer optical fiber (POF) has been created. The novel grating has a length of 1 cm with a reflectivity of 80% and a linewidth of about 0.5 nm. The wavelength tunability of the POF grating by stretching was investigated and a wavelength tunable range of 20 nm has been achieved. Based on the properties of the polymer, we believe that this kind of grating has a wavelength tuning potential of more than 100 nm.

Highly tunable Bragg gratings in single-mode polymer optical fibers

Smart technology for textiles and clothing - an overview and review. Electrically active polymer materials: application of non-ionic polymer gel and elastomers for artificial muscles. Heat storage and thermo-regulated textiles and clothing. Thermally sensitive materials. Cross-linked polyol fibrous substrates as multifunctional and multi-use intelligent materials. Stimuli-responsive interpenetrating polymer network hydrogels composed of poly(vinyl alcohol) and poly(acrylic acid. Permeation control through stimuli-responsive polymer membrane prepared by plasma and radiation grafting techniques. Mechanical properties of fibre Bragg gratings. Optical responses of FBG sensors under deformations. Smart textile composites integrated with fibre optic sensors. Hollow fibre membranes for gas separation. Embroidery and smart textiles. Adaptive and responsive textile structures (ARTS. Wearable technology for snow clothing. Bio-processing for smart textiles and clothing. Tailor-made intelligent polymers for biomedical applications. Textile scaffolds in tissue engineering.

Smart fibres, fabrics and clothing

Proliferation of aligned mammalian cells on laser-nanostructured polystyrene.

UV laser ablation of polymers was discovered 20 years ago.1,2 This effect has many fascinating applications in lithography, micromechanics, and medicine. For the last 20 years, more than 103 papers describing this phenomenon were published (see, e.g., comprehensive reviews, refs 3-7). Despite the high research activity, the nature of UV laser ablation of polymers is still far from being fully understood, e.g., one can find contradictory interpretations of the same results in different papers. Originally, UV laser ablation of polymers was believed to be a pure photochemical effect, resulting from the direct bond breaking by UV photons.8-10 Gradually, investigators obtained evidence that laser heating of materials is significant and a pure thermal nature of laser ablation was considered.11-13 Here we use the term “photothermal”7 for the process resulting from laser heating of material. Polymers are complex materials; therefore, laser ablation of polymers is also a complicated phenomenon. In this paper, we will focus on the models of laser ablation. In addition, we inevitably have to answer the question of what are the specific features of laser ablation of polymers that distinguish them from the laser ablation of other materials (metals, semiconductors, inorganic dielectrics, molecular solids). There are several approaches to modeling of polymer ablation. The authors of this paper represent one of the “schools”; thus, our view of the problem is somewhat subjective. Despite the complex nature of laser ablation, we prefer to develop simplified models (e.g., “pure” photochemical or “pure” photothermal), and analyze them in detail to be able to assign specific features, which are experimentally observed for a particular ablation mechanism. We start with the photochemical model. In fact, the first consideration of laser ablation10 employed a very simple but constructive idea that takes into account the specific feature of polymer materials. This idea is that polymers consist of long molecular chains with strong, covalent, bonds inside. At the same time, molecules belonging to different chains interact weakly. Therefore, polymer material becomes simple molecular solid (i.e., easily removed material), if we break the long polymer chains into small pieces by direct photochemical effect (UV photons are considered to have energy pω exceeding the energy of * Corresponding author, e-mail: bit@appl.sci-nnov.ru. † Institute of Applied Physics Russian Academy of Sciences. ‡ Data Storage Institute. 519 Chem. Rev. 2003, 103, 519−552

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Models for laser ablation of polymers.

For the first time, pure laser induced periodic structures (without any ablation or any larger structure) of submicron size (spacing and amplitude of 0.2 μm) are developed on polymer surfaces [poly(ethylene terephthalate), poly(butylene terephthalate) and polystyrene] by irradiation with one thousand pulses of the polarized beam of the excimer laser (193 and 248 nm). Fluence is below the ablation threshold and must be chosen in a narrow window which depends on the polymer and the wavelength. The obtained relief is observed by SEM, TEM and characterized by ellipsometry. Structures are obtained also by irradiation of thin films (2000 A) coated on silicon wafers.

Submicron periodic structures produced on polymer surfaces with polarized excimer laser ultraviolet radiation

The solid-state polycondensation of poly(ethylene terephthalate) (PET) amorphous and unoriented films from Du Pont (precursor for their Mylar® 1 polyester film) prepared from a specified catalyst and monomer system has been studied. The effect of various reaction parameters such as reaction temperature and time on inherent viscosity (ηinh) and number of carboxy and hydroxy end-groups has been investigated. From ηinh measurements an empirical equation was taken which allows the calculation of (Mn) of PET film after solid-state polycondensation at a certain temperature and time. The melting behaviour of the solid-state polycondensated samples was also studied.



Die Festphasen-Polykondensation von amorphen, unorientierten Poly(ethylenterephthalat)-Folien (PET) (Vorstufe der Du Pont Mylar®1 -Polyesterfilme), die mit einem speziellen Katalysator-und Monomer-System hergestellt wurden, war Gegenstand dieser Arbeit. Der Einflus verschiedener Reaktionsparameter, wie Reaktionstemperatur und -zeit, auf die inharente Viskositat (ηinh) und auf die Anzahl der Carboxy-und Hydroxy-Endgruppen wurde untersucht. Aus den Messungen von ηinh wurde eine empirische Gleichung erstellt, die die Berechnung von Mn der PET-Folien nach der Festphasen-Polykondensation bei gegebener Zeit und Temperatur erlaubt. Das Schmelzverhalten verschiedener Festphasen-Polykondensate wurde ebenfalls untersucht.

Solid‐state polycondensation of poly(ethylene terephthalate) films

A metallized composite sheet having low emissivity formed by coating a metallized moisture vapor permeable sheet with at least one outer inorganic coating layer, wherein the moisture vapor permeability of the composite sheet is at least about 80% of the moisture vapor permeability of the starting sheet.

Porous metallized sheets coated with an inorganic layer having low emissivity and high moisture vapor permeability

Effect of some current antioxidants on the thermo-oxidative stability of poly(ethylene terephthalate)

SUMMARY A series of poly(ethy1ene terephthalate) (PET) samples was prepared from dimethyl terephthalate and ethylene glycol. In each sample a phosphorous compound was added as heat stabilizer after the transesterification and before the polycondensation. These compounds were: phosphoric acid, tributyl phosphate, triphenyl phosphate, phenylphosphonic acid, phenylphosphinic acid, and sodium phenylphosphinate. Firstly, their interference with the transesterification catalyst was examined. Their stabilization effect was estimated by DSC analysis in nitrogen and air. Various thermal criteria have been used, such as stabilization coefficient and induction period of oxidation. Under the conditions used for polymerization, the more efficient stabilizers were tributyl phosphate, phenylphosphonic and phenylphosphinic acid. ZUSAMMENFASSUNG: Es wurde eine Reihe von Poly(ethylenterephthalat)(PET)-Proben aus Dimethylterephthalat und Ethylenglykol hergestellt. Bei jeder Probe wurde nach der Umesterung und vor der Polykondensation eine Phosphorverbindung als thermischer Stabilisator hinzugefugt. Diese Verbindungen waren: Phosphorsaure, Tributylphosphat, Triphenylphosphat, Phenylphosphorsaure, Phenylphosphonsaure und Natriumphenylphosphinat. Der Stabilisierungseffekt wurde durch DSC unter Stickstoff und Luft ermittelt. Es wurden verschiedene thermische Kriterien benutzt, wie Stabilitatskoeffizient und Induktionsperiode der Oxidation. Die besten Ergebnisse unter den durchgefuhrten Bedingungen wurden mit Tributylphosphat, Phenylphosphonsaure und Phenylphosphinsaure erhalten.

Aloyse Wilmes

Papers

Submicron periodic structures produced on polymer surfaces with polarized excimer laser ultraviolet radiation

Solid‐state polycondensation of poly(ethylene terephthalate) films

Porous metallized sheets coated with an inorganic layer having low emissivity and high moisture vapor permeability

Effect of some current antioxidants on the thermo-oxidative stability of poly(ethylene terephthalate)

Effect of some phosphorous compounds on the thermo-oxidative stability of poly(ethylene terephthalate)