Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1999-06-25
2002-07-02
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S064000, C521S142000, C521S150000, C521S183000
Reexamination Certificate
active
06414043
ABSTRACT:
BACKGROUND OF INVENTION
The present invention generally concerns compositions comprising pores (interstitial spaces) and voids wherein the voids are much larger than the mean pore size, optionally with the voids arranged in crystalline colloidal arrays (CCA) of spherical water voids (HCCA); methods of making said compositions; and methods of using the compositions to partition macromolecules. Preferably these compositions comprise hydrogels and preferably the voids are monodisperse. The size, number density, periodicity, and morphology of these voids can be well controlled by tailoring the original colloids. Because the voids are much larger than the mean size of the hydrogel pores, the hydrogel voids can serve as entropic traps. Flexible macromolecules such as linear polymers, proteins and nucleic acid fragments that may be present in these materials preferentially partition in the embedded voids, since they can maximize their chain conformational freedom, and thus their conformational entropy. As a result, flexible macromolecules will be entrapped preferentially in the designed voids rather than the rest of the hydrogel matrix. This entropic trapping strongly depends upon the size of the macromolecules, the voids, and the mean dimension of the hydrogel network.
The partitioning of a flexible polymer chain, such as a protein, between different volume elements (i.e., voids and pores) of a porous medium is important in areas such as size exclusion chromatography, gel electrophoresis, filtration, membrane separation, in controlled released drugs and other materials, and semi-homogeneous catalytic reactors in synthetic applications. Although intrinsically a thermodynamic phenomenon, such partitioning often plays an important role in many dynamic processes such as diffusion and electrophoretic migration of polymer chains through porous media. See, Nemoto, N., Kishine, M., Inoue, T., Osali, K.,
Macromolecules
, 1990, 23, 659-664; Kim, H., Chang, T., Yohanan, J. M., Wang, L., Yu, H.,
Macromolecules
, 1986, 19, 2737-2744; Smisek, D. L., Hoagland, D. A.,
Science
, 1990, 248, 1221-1223; Arvanitidou, E., Hoagland, D.,
Phys. Rev. Lett
., 1991, 67, 1464-1466; Lodge, T. P., Rotstein, N. A.,
Macromolecules
, 1992, 25, 1316-1325; Muthukumar, M., Hoagland, D. A.,
Macromolecules
, 1992, 25, 6696-6698, Mayer, P., Slater, G. W., Drouin, G.,
Appl. Theoret. Electrophoresis
1993, 3, 147-155; Rousseau, J., Drouin, G., Slater, G. W.,
Phys. Rev. Lett
., 1997, 79, 1945-1948; Guillot, G., Léger, L., Rondelez, F.,
Macromolecules
, 1985, 18, 2531-2537.
In the absence of specific interactions between the polymer chains and the media, it has been suggested that the volume-constrained chain conformational entropy controls the partitioning of flexible polymer chains between regions of different volumes. See Baumgärtner, A., Muthukumnar, M. J.,
Chem. Phys
., 1987, 87, 3082-3088; Muthukumar, M., Baumgärtner, A.,
Macromolecules
, 1989, 22, 1937-1941; Muthulcumar, M., Baumgärtner, A.,
Macromolecules
, 1989, 22, 1941-1946; Casassa, E. F.,
Polymer Left
., 1967, 5, 773-778; Casassa, E. F., Tagami, Y.,
Macromolecules
, 1969, 2, 14-26; Noolandi, J., Rousseau, J., Slater, G. W.,
Phys. Rev. Lett
., 1987, 58, 2428-2431; Slater, C. W., Wu, S. Y.,
Phys. Rev. Lett
., 1995, 75, 164-167; Daoud, M., De Gennes, P. G.,
J Phys
. (Les Ulis, Fr.), 1977, 38, 85-93; and Brochard, F., De Gennes, P. G.,
J Chem. Phys
., 1977, 67, 52-56.
FIG. 1
illustrates a polymeric gel system where the average network matrix provides only narrow channels
13
where the polymer
10
chain must be elongated; the polymer chain
10
is constrained with only limited conformational possibilities. In contrast, if the polymer chain
16
occupied a large spherical void,
15
it would be able to adopt all of its possible conformations, and would possess a larger conformational entropy. Consequently, the polymer chain should preferentially partition into this large void. From a dynamic point of view, if the polymer chain tries to leave the void, it encounters an entropic barrier since its conformations must be restricted to those which can squeeze into the narrow channels. Thus, ski large voids in a porous medium have been proposed to function as “entropic traps” to retard the diffusion and transportation of flexible polymer chains.
Evidence for this entropic trapping phenomenon has come from experimental studies on diffusion or low field electrophoretic migration of flexible chain polymers, in various types of porous media, such as entangled solutions, crosslinked polymeric gel networks, and model membranes of well-controlled pores. See, Nemoto, N., Kishine, M., Inoue, T., Osaki, K.,
Macromolecules
, 1990, 23, 659-664; Kim, H., Chang, T., Yohanan, J. M., Wang, L., Yu, H.,
Macromolecules
, 1986, 19, 2737-2744; Smisek, D. L., Hoagland, D. A.,
Science
, 1990,248, 1221-1223; Arvanitidou, E., Hoagland, D.,
Phys. Rev. Lett
., 1991, 67, 1464-1466; Lodge, T. P., Rotstein, N. A.,
Macromolecules
, 1992, 25, 1316-1325; Muthulcumar, M., Hoagland, D. A.,
Macromolecules
, 1992, 25, 6696-6698, Mayer, P., Slater, G. W., Drouin, G.,
Appl. Theoret. Electrophoresis
, 1993, 3, 147-155; Rousseau, J., Drouin, G., Slater, G. W.,
Phys. Rev. Lett
., 1997, 79, 1945-1948; and Guillot, G., Léger, L., Rondelez, F.,
Macromolecules
, 1985, 18, 2531-2537. It was observed that, when the equilibrium dimension of the macromolecules was comparable to the mean pore size of the medium and the electric field was weak, the diffusion constant (D) and electrophoretic mobility (&mgr;) depended more strongly on molecular weight than predicted by either Rouse dynamics or a reptation model. This behavior was rationalized by an entropic barrier transport model which was first formally proposed by Muthukumar and co-workers. See, Baumgärtner, A., Muthukumar, M. J.,
Chem. Phys
., 1987, 87, 3082-3088; Muthukumar, M., Baumgärtner, A.,
Macromolecules
1989, 22, 193 7-1941; and Muthukumar, M., Baumgärtner, A.,
Macromolecules
, 1989, 22, 1941-1946.
Casassa was the first to calculate, from ideal random walk statistics of chain conformational entropy, the equilibrium partition coefficients of a single polymer chain between confining volumes of different shapes (i.e. spherical, cylindrical, and slabshaped, etc.). See, Casassa, E. F.,
Polymer Lett
., 1967, 5, 773-778; and Casassa, E. F., Tagami, Y.,
Macromolecules
, 1969, 2, 14-26. A scaling argument for polymer solutions has been used to investigate both the partitioning and transport properties of self-avoiding polymer chains in good solvents in small cylindrical tubes as a function of concentration ranging from the dilute solution regime to the entanglement regime. See, De Gennes, P. G.,
Scaling Concepts in Polymer Physics
, Cornell University Press: Ithaca, N.Y., 1979; Daoud, M., De Gennes, P. G.,
J Phys
. (Les Ulis, Fr.), 1977, 38, 85-93; and Brochard, F., De Gennes, P. G.,
J Chem. Phys
., 1977, 67, 52-56.
The dynamics of both non-self-avoiding and self-avoiding polymer chains in various two-dimensional or three-dimensional model porous media have been studied by formalisms such as Monte Carlo methods, see, Baumgärtner, A., Muthukumar, M. J.,
Chem. Phys
., 1987, 87, 3082-3088; Muthukumar, M., Baumgärtner, A.,
Macromolecules
, 1989, 22, 1937-1941; Muthukumar, M., Baumgärtner, A.,
Macromolecules
, 1989, 22, 1941-1946, biased reptation model, see, Noolandi, J., Rousseau, J., G. W.,
Phys. Rev. Lett
., 1987, 58, 2428-2431; Slater, G. W., Wu, S. Y.,
Phys. Rev. Lett
., 1995, 75, 164-167; Daoud, M., De Gennes, P. G.,
J Phys
. (Les Ulis, Fr.), 1977, 38, 85-93; Brochard, F., De Gennes, P. G.,
J Chem. Phys
., 1977, 67, 52-56; Daoudi S., Brochard, F.,
Macromolecules
, 1978, 11, 751-758; De Gennes, P. G.,
Scaling Concepts in Polymer Physics
. Cornell University Press: Ithaca, N.Y., 1979; Carmesin, I., Kremer, K.,
Macromolecules
, 1988, 21, 2819-2823; and Zimi, B. H.,
Phys. Rev. Lett
., 1988, 61, 2965-2968, Brownian dynamics, see, Nixon, G. I., Slater, G. W.,
Phys. Rev. E
, 1996, 53, 4969-4980, and bond fluctuation algorithms,
Asher Sanford A.
Liu Lei
Baker & Botts LLP
Cooney Jr. John M.
University of Pittsburgh
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