Polymer films

Details Polymer films Polymer films

2000-11-15

2004-05-25

Zacharia, Ramsey (Department: 1773)

Stock material or miscellaneous articles

Composite

C428S474400, C428S480000, C428S500000, C428S522000, C428S524000, C428S532000

Reexamination Certificate

active

06740409

ABSTRACT:

BACKGROUND
The present invention relates to polymer films, their assembly, and their controlled destruction.
Polymer films find wide-ranging uses, from non-linear optics to electronic coatings. One way to produce polymer films is through self-assembly of the films, layer-by-layer. This self-assembly relies on electrostatic charge, of alternating sign, in each layer; charges of opposite sign in each layer attract, directing the self-assembly process. The layers may be build up from a solution, and in the assembly process, molecules may become trapped between the layers.
It would be desirable to destroy the polymer films in a controlled fashion, to release the molecules trapped between the layers. Molecules, such as drugs or dyes, could be trapped in the polymer films during the assembly process, and then released during controlled destruction of the polymer films. However, the layers of known self-assembled polymer films contain alternating charge, and therefore any controlled method of destruction of these films would require eliminating or reducing charge on some or all of the layers, in order to overcome the electrostatic attraction that holds the layers together, and to do so is not practical.
BRIEF SUMMARY
In a first aspect, the present invention is a film including a first polymer, and a second polymer hydrogen bonded to the first polymer.
In a second aspect, the present invention is a film including a first polymer having a plurality of hydrogen bond donating moieties, and a second polymer having a plurality of hydrogen bond accepting moieties.
In a third aspect, the present invention is a method of forming a film, including contacting a surface with a first polymer having a plurality of hydrogen bond donating moieties, and contacting the surface with a second polymer having a plurality of hydrogen bond accepting moieties.
DETAILED DESCRIPTION
The present invention includes a polymer film in which the layers are held together by hydrogen bond formation between the layers. The formation of the hydrogen bonds drives a self-assembly process. The attraction of the layers to each other can be overcome by creating charge on at least some of the layers, the charge creating a repulsive force, or increasing the solubility of the polymers while in contact with a solvent. In the case of creating charge, when the repulsive force between layers exceeds the attractive force from the hydrogen bonds, the polymer film will be destroyed, releasing molecules trapped in the polymer film. Through control of environmental factors, the creation of charge on the layers can be controlled, allowing for controlled destruction of the polymer film, and thereby controlled release of molecules trapped in the film. Unlike films formed in the past, the films are not made of polymers which each contain charged groups of opposite signs; these past films used the electrostatic attraction of the oppositely charged groups to bond the polymers together into the films.
The polymers used to form the films of the present invention include up to three moieties: a hydrogen bond donor, a hydrogen bond acceptor, and optionally, a charge-forming group. Each polymer used must include at least a hydrogen bond donor or a hydrogen bond acceptor; preferably at least one of the polymers used in the film contains a charge-forming group. Preferably, the film is produced using two polymers, with one polymer containing hydrogen bond donors, and the other polymer containing hydrogen bond acceptors, and at least one of the two polymers containing charge-forming groups. In the alternate embodiment of three, or more polymers, each polymer must contain at least hydrogen bond donors or hydrogen bond acceptors; at least one of the polymers used must also contain a charge-forming group.
A hydrogen bond is a relatively weak secondary interaction between a hydrogen atom bound to a more electronegative atom and another atom that is also generally more electronegative than hydrogen and has one or more lone electron pairs, enabling it to act as a base. Hydrogen bonding has been extensively studied (see, for example, “Advanced Inorganic Chemistry” 5th ed., F. Albert Cotton and Geoffrey Wilkinson, pp.90-94 (John Wiley & Sons, 1988)).
Hydrogen bond donors are moieties that contain at least one hydrogen atom that may participate in hydrogen bond formation, and a more electronegative atom bound to the hydrogen atom. Examples of these moieties include, preferably, O—H and N—H, and less preferably, P—H, S—H. The moiety C—H may also, less preferably, be a hydrogen bond donor, when the carbon atom is bond to another atom through a triple bond, when the carbon atom is bound through a double bond to O, or when the carbon atom is bound to at least two atoms selected from O, F, Cl and Br.
Hydrogen bond acceptors are moieties that contain an atom more electronegative than hydrogen that also has a lone pair of electrons. Examples of these atoms include preferably N, O and F, and less preferably Cl, Br, I, S and P. Examples of hydrogen bond acceptor moieties include C═O, O—H, N—H, C—F, P═O and C≡N.
Charge forming structures are moieties that can develop charge when exposed to one or more environmental changes. Examples of environmental changes are a change in pH, a change in ionic strength, exposure to an electric field, or exposure to dissolved ions. Examples of moieties that can develop charge under changing pH conditions include acid or base moieties. Examples of moieties that can develop charge under exposure to an electric field include carboxylic acids. Examples of moieties that can develop charge under exposure to dissolved ions include crown ethers (upon exposure to certain alkali metal ions).
Polymers for use in the present invention include polymers containing hydrogen bond donors and/or hydrogen bond acceptors, for example polycarboxylic acids such polyacrylic acid and polymethacrylic acid; polynucleotides such as poly(adenylic acid), poly(uridylic acid), poly(cytidylic acid), poly(uridylic acid) and poly(inosinic acid); polymers of vinyl nucleic acids such as poly(vinyladenine); polyamino acids such as polyglutamic acid and poly(&egr;-N-carbobenzoxy-L-lysine); polyalcohols such as poly(vinyl alcohol); polyethers such as poly(ethylene oxide), poly(1,2-dimethoxyethylene), poly(vinylmethyl ether), and poly(vinylbenzo-18-crown-6); polyketones and polyaldehydes such as poly vinyl butyral and poly(N-vinyl-2-pyrrolidone); polyacrylamides such as polyacrylamide, polymethacrylamide and poly(N-isopropylacrylamide); polyamines such as poly(4-amine)styrene; polyesters such poly(cylohexane-1,4-dimethylene terephthalate) and polyhydroxy methyl acrylate; polyphosphazenes such as poly(bis(methylamino)phosphazene) and poly(bis(methoxyethoxyethoxy)phosphazene; polysaccharides such as carboxymethyl cellulose; and copolymers thereof,
Some examples of preferable pairs of polymer for forming films include those of the following types:
Type 1. Homopolymer of polycarboxylic acid, paired with the specified Polymer B.
Polymer A
Polymer B
Polycarboxylic acid
Poly(ethylene oxide)
Polycarboxylic acid
Poly(1,2-dimethoxyethylene)
Polycarboxylic acid
Poly(vinylmethyl ether)
In the above three examples of Polymer B, the motif of proton acceptance in hydrogen bonding, is O . . . HO.
Polymer A
Polymer B
Polycarboxylic acid
Poly(N-vinyl-2-pyrrolidone) (PVP)
Polycarboxylic acid
Poly(vinyl alcohol)
Polycarboxylic acid
Polyacrylamide
Polycarboxylic acid
Poly(N-isopropylacrylamide)
Polycarboxylic acid
(CH
2
(NCOCH
3
)CH
2
)
x
In the above five examples of Polymer B, the motif of proton acceptance, is NC═O . . . HO.
Films formed from these pairs of polymers may be dissolved (the films destroyed) at high pH or in dimethylsulfoxide (DMSO). A film formed from PMA-PVP is stable in tetramethylurea and dimethylformamide (DMF) and dissolves in dimethylacetamide, N-methylpyrrolidone and hexamethylphosphoric triamide. The stability of these films can also be affected by temperature; these films become more stable as the temperature increases in water, but are destabilize

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