Etching a substrate: processes – Etching to produce porous or perforated article
Reexamination Certificate
2002-01-24
2003-12-09
Alanko, Anita (Department: 1765)
Etching a substrate: processes
Etching to produce porous or perforated article
C427S243000, C427S244000, C427S508000, C436S518000, C436S531000, C521S061000
Reexamination Certificate
active
06660176
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention pertains to molecular imprinting of small particles and, more particularly, to a method of molecular imprinting which utilizes a propellant as the solvent and dispersing agent of the matrix material and to imprinted particles formed by the method as well as devices coated with imprinted particles, such as, for example, surface acoustic wave (SAW) devices. In addition, the invention pertains to a method for the formation of small particles of monomers containing solid-state reactivity.
2. Description of the Prior Art
Molecular imprinting is a process, which involves arranging of polymerizable functional monomers around a template (print) molecule. This is achieved either by utilizing non-covalent interactions such as hydrogen bonds, ion-pair interactions, etc. (non-covalent imprinting), or by reversible covalent interactions (covalent imprinting) between the print molecule and the functional monomers. Typically, a molecule to be imprinted (template) is combined with a mixture of functionalized and non-functionalized monomers so that the monomers surround the template. In the process, functionalized monomers align themselves in a binding relationship to complementary functional groups on the template to form therefore a complex with the template. After polymerization, functional groups are held in position by the highly cross-linked polymeric matrix. The template is then removed, and the resulting material contains imprinted binding sites which are complimentary in size and shape to the template. The complementary binding groups, arising from the functionalized polymer groups incorporated during the imprinting, are specifically positioned to enhance the preferential substrate binding and, if desired, subsequent catalysis. The imprinted polymer materials are capable of specific sorption or specific catalytic activity. A good description of state of the art of molecular imprinting can be found in Mosbach, K., Trends in Biochemical Sciences, Vol. 7, pp. 92-96, 1994; Wulff, G., Trends in Biotechnology, Vol. 11, pp. 85-87, 1993; and Andersson, et al., Molecular Interactions in Bioseparations (Ngo. T. T. ed.), pp. 383-394.
The functionalized monomers usually used for molecular imprinting are: acrylic acids [Anderson, L.; Sellergren, B; Mosbach, K Tetrahedron Lett. 1984, 25, p.5211. Sellergren, B.; Lepisto, M.; Mosbach, K.
J. Am. Chem. Soc.
1988, 110, p.5853. Andersson, L. I.; Mosbach, K.
J. Chromatogr.
1990, 516, p.313. Matsui, J.; Miyoshi, Y.; Takeuchi, T.
Chem. Lett.
1995, p.1007.], vinylbenzoic acids [Andersson, L.; Sellergren, B.; Mosbach, K.
Tetrahedron Lett.
1984, 25, p.5211], acrylamino-sulfonic acids [Dunkin, 1. R.; Lenfeld, J.; Sherrington, D. C.
Polymer
1993, 34, p.77], amino-metacrylamides [Beach, J. V.; Shea, K. J.
J. Am. Chem. Soc.
1994, 116, p.379.], vinylpyridines [Ramstrom, O.; Andersson, L. I.; Mosbach, K.
J. Org Chem.
1993, 58, p.7562. Kempe, M.; Fischer, L.; Mosbach, K.
J. Mol. Recognit.
1993, 6, p.25], vinyl imidozales [Kempe, M.; Fischer, L.; Mosbach, K.
J. Mol. Recognit.
1993, Vol. 6, p.25. Leonhardt, A.; Mosbach, K.
React. Polym.
1987, 6, p.285.], acrylamides [Yu, C.; Mosbach, K.
J. Org Chem.
1997, 62, p.4057.], and vinyl-iminodiacetic acids [Dhal, P. K.; Arnold, F. H.
J. Am. Chem. Soc.
1991, 113, p.7417. Kempe, M.; Glad, M.; Mosbach, K.
J. Mol. Recognit
1995, 8, p.35.].
Prior to this invention, methods of molecular imprinting have achieved only modest success in the enhancing polymer selectivity and catalytic activity. The reason for this is, that in order to be effective in a wide scale, imprinted materials must have binding/active sites to be homogeneous (in specificity and activity), be well formed (based on shape and reactivity), and be easily accessible by the reactant molecules (access is affected by shape, size and polarity of the channels leading to the catalytic site). The imprinted polymeric materials created by prior art methodologies have sites that are generally not very accessible and not homogenous, as they often have different binding affinities and/or reactivities. These problems mainly arise from the method used for producing the imprinted polymer particles.
A common method of molecular imprinting is referred to as solution polymerization. This method results in the formation of imprinted sites that are completely encased within the polymer. In order to enable an access to those sites, the polymer monolith must be subjected to mechanically grinding to produce particles that have exposed sites. Grinding produces irregularly shaped particles and typically only less than 50 percent (50%) of the ground polymer is recovered as useable particles with size less than 25 &mgr;m. Irregular particles generally give less efficient devices mainly because of the deformation of a large number of the binding sites. As a result, damage to the sites adversely affects their selectivity and activity. An alternative method to increase accessibility to the imprinted sites is by the use of porogen compounds which are known to generate foam-like polymer structures when combined with polymer forming materials. Porogens, which are typically inert solvents, are mixed with the polymerizable monomers during the imprinting process and are washed away after polymerization is complete. This creates large pores that allow access to the created binding sites. However, while the porogens are removed, some of the structural integrity of the polymer can be lost at the same time, leading to the deformation of the sites and loss in specificity and activity.
Another alternative for molecular imprinting is by direct polymerization of particles in liquid media. Surfactants are used to create molecular microstructures, such as micelles or reverse micelles. Then, inorganic or organic monomers are polymerized around those molecular microstructures at the surfactant-solvent interface to form polymer beads, dispersed in the liquid media to prevent agglomeration. The size and shape of the formed beads highly depend on the chemistry of the mixture and reaction conditions, such as temperature and stirring. When the surfactant is removed, the remaining material has a size and shape complementary to the size and shape of the initial molecular microstructures. By controlling variables such as surfactant selection and concentration, a variety of different microstructure shapes such as micellar, cubic, tetragonal, lamellar, tubular and reverse micellar can be formed. Consequently, monodisperse particles of a variety of different sizes and porous materials with a variety of different shapes of pores and channels can be created. Methods of making porous material are described, for example, in the following patents each of which are incorporated herein by reference: U.S. Pat. No. 5,250,282 to Kresge et al; U.S. Pat. No. 5,304,363 to Beck et al; U.S. Pat. No. 5,321,102 to Loy et al; U.S. Pat. No. 5,538,710 to Guo et al; U.S. Pat. No. 5,622,684 to Pennavaia et al; U.S. Pat. No. 5,750,085 to Yamada.
Molecular imprinting by direct polymerization of particles in liquid media is more advantageous, but still has limitations due to the liquid media needed to disperse particles to prevent particles agglomeration. Therefore, after polymerization, particles need to be separated from the liquid media for further use, which is not an easy task, especially for small particles. While in many applications, imprinted polymers should be deposited on the special surfaces, such as in chemical and biological sensors, and in chromatography and filtration devices. Deposition of the imprinted polymer material and adherence on the surface remains a big problem.
U.S. Pat. No. 5,587,273 to Yan et al., which is herein incorporated by reference, describes a way of molecular imprinting of polymer film directly on the surface of sensor. The invention describes molecularly imprinted substrate and sensors employing the imprinted substrate for detecting the pres
Levit Natalia
Pestov Dmitry
Tepper Gary
Wnek Gary
Alanko Anita
Virginia Commonwealth University
Whitham Curtis & Christofferson, P.C.
LandOfFree
Molecular imprinting of small particles, and production of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Molecular imprinting of small particles, and production of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Molecular imprinting of small particles, and production of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3144583