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Micromachining was performed in polymethylmethacrylate (PMMA) using X-ray lithography for the fabrication of miniaturized devices (microchips) for potential applications in chemical and genetic analyses. The devices were fabricated using two different techniques: transfer mask technology and a Kapton mask. For both processes, the channel topography was transferred (1:1) to the appropriate substrate via the use of an optical mask. In the case of the transfer mask technique, the PMMA substrate was coated with a positive photoresist and a thin Au/Cr plating base. Following UV exposure, the resist was developed and a thick overlayer (approximately 3 microns) of Au electroplated onto the PMMA substrate only where the resist was removed, which acted as an absorber of the X-rays. In the other technique, a Kapton film was used as the X-ray mask. In this case, the Kapton film was UV exposed using the optical mask to define the channel topography and following development of the resist, a thick Au overlayer (8 microns) was electrodeposited onto the Kapton sheet. The PMMA wafer during X-ray exposure was situated directly underneath the Kapton mask. In both cases, the PMMA wafer was exposed to soft X-rays and developed to remove the exposed PMMA. The resulting channels were found to be 20 microns in width (determined by optical mask) with channel depths of approximately 50 microns (determined by x-ray exposure time). In order to demonstrate the utility of this micromachining process, several components were fabricated in PMMA including capillary/chip connectors, injectors for fixed-volume sample introduction, separation channels for electrophoresis and integrated fiber optic fluorescence detectors. These components could be integrated into a single device to assemble a system appropriate for the rapid analysis of various targets.

The synthesis of copolycarbonates with high aliphatic contents for possible applications as optical plastics is described. Copolymers of 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol (TMCBD) with a series of 14 bisphenol derivatives were prepared and characterized. The refractive index of these materials varies from 1.49 for the 2,2‐hexafluoropropane substituted copolymer to 1.57 for the 9,9‐fluorene substituted copolymer; thus, all of the copolymers exhibit lower refractive indices than the bisphenol A homopolycarbonate. The glass tran‐sition temperatures of the copolymers vary from 110 to 210°C; the beta transition tem‐peratures vary from ‐70 to 0°C when measured at 10 Hz by dynamic mechanical analysis. The copolymers exhibited good thermal stability (0–3% weight loss) when heated above the glass transition temperature, and only undergo extensive decomposition (80–90%) at 300–360°C. © 1995 John Wiley & Sons, Inc.

A series of aliphatic polycarbonates based on the condensation copolymerization of the bischloroformate of 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TMCBD) with itself and the diols of 3-cyclohexene-1,1-dimethanol, 1,4-cyclohexanediol (CHD), in various molar ratios, exo,exo-tricyclo[2.2.1.02,6]heptane-3,5-diol, and 4,8-bis(hydroxymethyl)tricyclo[5.2.102,6]decane (BTD) were synthesized. Incorporation of cyclic and tricyclic repeat units produced polycarbonates with high glass transition temperatures (T g's), high molecular weights, and low refractive indexes. The crystallinity of the TMCBD homopolymer was minimized in the CHD/TMCBD copolymers with little effect on T g but with decreased thermal stability. Thermal analysis yields decomposition temperatures ranging from 354 °C for the TMCBD homopolymer to 292−298 °C for the CHD/TMCBD copolymers; all polymers undergo complete thermal degradation. Refractive indexes range from 1.493 for the 1:1 copolymer of BTD and TMCBD to 1.481 for the CHD/TMCBD copolymers. Thin films composed of an aliphatic polycarbonate and a base-releasing cobalt(III) photoinitiator can be imaged with deep-UV light. The polycarbonates selected for study were the 9:1 copolymer of CHD and TMCBD and the 1:1 copolymer of BTD and TMCBD. The first step of image formation is the efficient photoredox decomposition of the photoinitiator with the release of multiequivalents of Lewis base. In the case of [Co(en)3](BPh4)3 (en is ethylenediamine, BPh4 - is tetraphenylborate), photogenerated ethylenediamine cross-links the polymer chains via formation of bis(dicarbamate) linkages. Development with solvent dissolves the unirradiated areas to yield negative-tone images. For [Co(NH3)6](BPh4)3, photoreleased ammonia causes chain scission in the exposed regions of the film, and wet or dry development results in positive-tone images.

The spreading of solutions of three trisiloxane surfactants on two hydrophobic substrates, polyethylene and polyvinylidenefluoride, was studied with the addition of 0–40 mass % of glycerol. It was found that all the surfactant solutions spread faster than silicone oil of the same viscosity, confirming the existence of a mechanism which accelerates the spreading of the surfactant solutions. For the non-superspreading surfactant, BT-233, addition of glycerol improved the spreading performance on polyvinylidenefluoride and resulted in a transition from partial to complete wetting on polyethylene. The fastest spreading was observed for BT-233 at a concentration of 2.5 g/L, independent of glycerol content. For the superspreading surfactants, BT-240 and BT-278, the concentration at which the fastest spreading occurs systematically increased with concentration of glycerol on both substrates from 1.25 g/L for solutions in water to 10 g/L for solutions in 40% glycerol/water mixture. Thus, the surfactant equilibration rate (and therefore formation of surface tension gradients) and Marangoni flow are important components of a superspreading mechanism. De-wetting of the solutions containing glycerol, once spread on the substrates, resulted in the formation of circular drop patterns. This is in contrast to the solely aqueous solutions where the spread film shrank due to evaporation, without any visible traces being left behind.