RECON is an algorithm for the rapid reconstruction of molecular charge densities and charge density-based electronic properties of molecules, using atomic charge density fragments precomputed from ab initio wave functions. The method is based on Bader's quantum theory of Atoms in Molecules. A library of atomic charge density fragments has been built in a form that allows for the rapid retrieval of the fragments and molecular assembly.
Present microelectronic photoimaging applications employ onium salts for deep UV (I-line, 365 nm) photolithography. Since most onium salts do not absorb at this wavelength, photosensitizers are commonly employed. Polynuclear aromatic hydrocarbons are the most efficient known examples of electron-transfer photosensitizers for onium salts. However, they have serious drawbacks that limit their use, such as they are expensive, toxis, and poorly soluable in most reactive monomers and polymer systems.
Interest and research activity in the photoinitiated cationic crosslinking polymerizations of multifunctional epoxide and oxetanes monomers have increased rapidly as this technology has found broad use in many industrial applications. However, while the synthesis of current epoxy-functional siloxanes yields monomers that undergo efficient cationic ring-opening photopolymerization to give crosslinked materials with excellent thermal and chemical resistance, they produce hard, brittle, glass-like materials with little elongation and flexibility.
As part of the continuing effort to reduce the environmental impact of various industrial chemical processes, there has been a strong emphasis in developing new methodology for the application and cure of organic coatings. While these ubiquitous materials are absolutely essential to modern life, they also constitute one of the primary industrial Sources of emissions of Volatile organic Solvents that contribute to air and water pollution.
This technology relates to a photopolymerizable class of vinyl ether oligomers which can find application in the areas of coatings, adhesives, printing inks, photoresists and high impact composites. The versatile photopolymerization capability makes these oligomers an excellent strategic candidate for shrinkage control coatings in place of acrylates. These oligomers include photopolymerizable functional groups which manifests excellent uniform film forming characteristics when cured by UV or electron beam radiation.
In photoinitiated cationic ring-opening polymerization, the polymerizable substrate is subjected to irradiation with light for a brief period during which the photopolymerization must proceed essentially to completion. Consequently, only monomers that undergo very high rates of polymerization may be employed. Certain epoxide monomers display high reactivity in photoinitiated cationic polymerization and are suitable for such uses while most other undergo sluggish reaction and are not usable.
There are two basic classes of adhesives in widespread current use. The first class is pressure sensitive adhesives, such as are employed in adhesive tapes. The second class is reactive adhesives, used primarily for structural purposes. A long-standing problem with these types of adhesives is that they are unable of obtaining both a long working life and a rapid cure time.
This invention is directed to a new, inexpensive analytical instrument that can be used to study and evaluate such essential parameters as light intensity, photoinitiator concentration, and monomer reactivity in a wide variety of UV photopolymerization curing applications. The device provides real-time information as the sample proceeds through the photoreactive phase. Through the direct, continuous, and remote monitoring of the sample using optical pyrometery, the temperature of the monomer undergoing photopolymerization can be obtained as a function of time.
Currently, the most common semiconductor dielectric is silicon dioxide (SiO2), which has a dielectric constant of about 4.0. There is a substantial interest in materials with low dielectric constants that can replace SiO2-based insulators as inter layer dielectrics (ILD). This invention is directed to a new process for the preparation of low dielectric constant films. The sol-gel process employs a hyperbranched polycarbosilane precursor that is applied to a substrate by spin coating.
Several methods for the preparation of polymeric microbeads for chromatographic separations in the pharmaceutical industry have been developed over the past several decades. However, those methods often result in microbeads with a wide distribution of sizes. This invention results in more uniform particle size but also microbeads that are derived from multifunctional epoxy monomers and that have residual epoxy functionality on their surfaces.