This work reviews the literature published over the last ten years on polymer mechanical properties as a function of molecular weight and molecular weight distribution, Thermal properties, stress‐strain properties, impact, fracture, fatigue, creep, stress relaxation and cracking and crazing are examined for a wide variety of homopolymers and a limited number of copolymers. In general, mechanical properties increase as the molecular weight increases. However, above some limiting molecular weight the mechanical property is usually unaffected. Although much work has been done to describe the effects of molecular weight on mechanical properties, little quantitative correlation exists. The available equations to predict such properties as cracking and crazing, Tg, Tm and tensile strength from molecular characteristics are discussed in detail. However, a more quantitative description incorporating a wider range of mechanical properties would be more useful. This would facilitate use of the vast amount of information available and enable it to be applied more readily to new polymer systems.

We report a procedure that uses microcontact printing and wet chemical etching to fabricate patterned films of indium tin oxide (ITO) and indium zinc oxide (IZO). The procedure consists of three steps: (1) inking a patterned elastomeric stamp with an alkanephosphonic acid; (2) microcontact printing to form a patterned multilayer film of alkanephosphonic acid on the surface of an ITO or IZO film; (3) etching the unprotected regions of the ITO or IZO film using 0.05 M oxalic acid as the etchant. We demonstrate this procedure by fabricating patterned ITO and IZO films with areas as large as 15 cm 2 and minimum feature sizes of ∼2 µm. The key step in this procedure is applying the alkanephosphonic acid ink to the surface of the stamp. We present two different inking methods to illustrate the impact of stamp inking on the quality of printed and etched ITO and IZO films.

Electroless-depositing a metal from solution to a substrate and patterning it using microcontact printing is an alternative to the conventional patterning of vacuum-deposited metals using photolithography. Here, we pattern Cu onto 15 × 15 sq-inch glass substrates by (i) self-assembly of a thin layer of amino-derivatized silanes to the glass, (ii) binding Pd/Sn catalytic particles to the silanes, (iii) electroless deposition of ∼120 nm of Cu on the catalytic surface, (iv) microcontact printing hexadecanethiol on the Cu film using an accurate printing tool, and (v) selectively etching the printed Cu using hexadecanethiol as a resist. This method is particularly attractive for the fabrication of metallic gates for thin-film transistor liquid-crystal displays.

The thin-film transistor (TFT) array of liquid-crystal displays (LCDs) comprises a number of metallic, semiconducting, and insulating layers, which need to be deposited and patterned accurately with very high yields on a (large) glass substrate. We are exploring how to fabricate the gate metal lines of the TFT array in an entirely new and potentially cost-effective waysby depositing the metal layer of the TFT array using electroless deposition (ELD) and by patterning the gates using microcontact printing (µCP). To achieve this goal, we separately explore first the plating conditions to deposit a gate metal on 15 in. glass substrates, and second the printing process to finally combine them later in the work. Here, we review in depth the metallization of the glass by ELD of NiB as gate material, and we demonstrate the patterning of the gate layer using a conventional photoengraving process (PEP, i.e., photolithography and wet etching). We selected NiB because this material can fulfill the conductivity requirements for making an SXGA (1280 pixels × 1020 pixels) display having a 157 pixel per inch resolution. Because ELD requires the presence of a catalyst on the substrate, we derivatized the glass by grafting 3-(2-aminoethylamino)propyltrimethoxysilane (EDA-Si) from an aqueous solution, which serves as linker between the glass and colloidal Pd/Sn particles. We identify the optimum conditions for the derivatization of the glass and to activate it with colloidal Pd/Sn in a uniform manner so as to electroless deposit high-quality NiB layers. We plated uniform NiB films of 120 nm thickness on both faces of 15 in. glass substrates, and we removed the NiB from one face of the substrate using HNO3 dissolved in water. The remaining NiB layer was patterned using a mask of photoresist and an etch bath comprising an aqueous solution of 3-nitrobenzenesulfonic acid (NBSA) and ethylenediamine (EDA) at pH ∼ 9. This etch system minimizes the galvanic coupling between the Pd/Sn particles and the NiB, and it enabled patterning the gates with an accuracy better than 1 µm. Annealing the NiB layer at 400 °C reduces its specific resistivity from 25 to 13 µΩ cm, and the roughness and adhesion of the layer to the glass enable the plasma deposition of silicon nitride (SiN x) and amorphous silicon (a-Si) layers over the patterned array of gates. Building an array of TFTs for a SXGA display using the NiB as the gate layer yielded transistors with transfer and output characteristics similar to those fabricated using a conventional gate material. The work presented here may spur the introduction of novel surface chemistry processes into flat-panel-display factories.

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