Lubricants for magnetic media

Amphiphilic compound having one of the following structures: EQU (X--T).sub.n --A--Y.sub.m and (X-T).sub.n --R--(T--A).sub.n wherein X is a fluorocarbon terminal group, T is a polar linking group, A is a nucleus other than saturated lower aliphatic, Y is a polar nonlinking group, R is a saturated or unsaturated, substituted or unsubstituted, straight or branched lower aliphatic group, n is at least one, and the sum of n and m is at least two. Such compounds are useful as lubricants for magnetic media. Also, a lubricated magnetic medium comprising a planar, polar surface covered with a monolayer comprising a compound having the structure described above, except that A can also be a saturated lower aliphatic group.

FIELD OF THE INVENTION 
The present invention relates generally to novel amphiphilic compounds. 
(Amphiphilic compounds are defined as compounds having at least one polar 
portion and at least one nonpolar portion, which are capable of forming 
Langmuir-Blodgett films.) The present invention relates more particularly 
to amphiphilic compounds in which each nonpolar portion is a fluorocarbon 
and each polar portion is capable of bonding to a polar surface. These 
compounds have utility as lubricants to protect metal, metal oxide, 
carbon, or other surfaces of thin film magnetic recording media useful in 
data, audio, and video recording from wear and corrosion. The present 
invention also relates to a novel thin-film magnetic medium comprising a 
polar surface of the magnetic medium, coated by and bonded to a monolayer 
of at least one of the present amphiphilic compounds. 
BACKGROUND OF THE INVENTION 
Magnetic media are used in the form of tapes, floppy disks, hard disks, and 
the like to store magnetic impulses received from a recording or write 
head scanned on the medium and to reconstruct the same impulses in a 
playback or read head scanned on the same part of the medium. The write 
and read functions of a computer disk system are commonly performed by a 
single read/write head. The head moves rapidly with respect to the 
magnetic medium and closely approaches it, momentarily coming into direct 
contact with it when the head starts or stops scanning. The industry has 
found it necessary to lubricate the magnetic medium so friction between 
the medium and head does not rapidly destroy the head or the medium. 
Computer data storage media such as oxide disks have been coated with a 30 
to 120 Angstrom layer of fluorinated oil to reduce friction while the head 
is in contact with the disk, and to protect the disk from corrosive 
atmospheric contaminants. This coating has worked well for systems 
achieving densities of no more than about 60 to 100 megabytes per square 
inch, wherein the read/write heads fly relatively high over the recording 
medium, riding on an air cushion. Other materials which have found utility 
as lubricants for magnetic media used with high-flying read-write heads 
include fluorinated oils (particularly perfluoropolyethers), fatty acids 
and their esters, organosilanes, and organoaminosilanes. 
In higher-density magnetic storage systems currently under development, the 
read/write heads will fly lower. The lubricant layer for such heads will 
typically be much thinner--perhaps less than 30 Angstroms thick. Such a 
thin layer of a conventional lubricant will not lubricate the magnetic 
medium sufficiently to allow it to withstand the increased friction 
resulting from repeated scanning by low-flying heads. 
Another problem in the art is degradation of the lubricant. Fatty aliphatic 
chains (broadly defined herein as those having from 6 to 22 carbon atoms) 
degrade with each read/write cycle, forming a buildup of sludge. This 
sludge causes higher friction between the magnetic medium and the head, 
head instability, and increased spacing between the head and the medium 
surface. Deterioration of performance is the practical result. 
Thus, a need has arisen for new lubricants which will durably adhere to the 
disk in thin layers, will allow repeated read/write cycles without an 
increase in friction or sludge buildup, will offer corrosion protection, 
and will provide better lubrication in the environment of a low flying 
read/write head. 
SUMMARY OF THE INVENTION 
One aspect of the invention is an amphiphilic compound having one of the 
following structures: 
EQU (X--T).sub.n --A--Y.sub.m and (X--T).sub.n --R--(T--A).sub.n 
wherein X is a fluorocarbon terminal group, T is a polar linking group, A 
is a nucleus other than saturated lower aliphatic, Y is a polar nonlinking 
group, R is a straight or branched, saturated or unsaturated, substituted 
or unsubstituted lower aliphatic group, n is at least one, and the sum of 
n and m is at least two. Such compounds are improved lubricants for 
magnetic media. 
Another aspect of the invention is a lubricated magnetic medium comprising 
a planar, polar surface covered with a monolayer comprising a compound 
having the structure described in the preceding paragraph, except that A 
includes saturated lower aliphatic groups in this embodiment of the 
invention. The present lubricants bond more tightly to the substrate, are 
less easily degradable, and provide better lubrication and corrosion 
protection than the lubricants of the prior art.

DETAILED DESCRIPTION OF THE INVENTION 
While the invention will be described in connection with certain preferred 
embodiments, it will be understood that the invention is not limited to 
the preferred embodiments. On the contrary, the invention includes all 
alternatives, modifications, and equivalents as may be included within the 
spirit and scope of the invention as defined by the appended claims. In 
the present disclosure, it is assumed that where more than one substituent 
of a particular kind is to be selected, each selection is made 
independently, so the several substituents of the same kind may be the 
same or different. 
The present compounds are amphiphilic compounds having a general structure 
selected from the group consisting of: 
EQU (X--T).sub.n --A--Y.sub.m and (X--T).sub.n --R--(T--A).sub.n 
X in each structure is broadly defined as a fluorocarbon. Exemplary 
fluorocarbons are selected from the group consisting of: 
i. branched or (preferably) straight-chain perfluoroalkyl moieties having 
from about 6 to about 22, preferably 6-12 carbon atoms. Several examples 
of this type are perfluoro-n-octyl (C.sub.8 F.sub.17 --), 
perfluoro-n-decyl (C.sub.10 H.sub.21 --), and perfluoro-n-dodecyl 
(C.sub.12 H.sub.25 --) moieties. 
ii. perfluoroalkyl-terminated lower aliphatic moieties including a 
perfluoroalkyl terminal group as described above and a straight or 
branched chain, saturated or unsaturated, unsubstituted or substituted 
lower aliphatic linking group having from 1 to about 5 aliphatic carbon 
atoms. The permissible substituents to the lower aliphatic linking group 
include lower aliphatic, cycloaliphatic, and aryl moieties as defined 
elsewhere herein and one or more heteroatomic substituents selected from 
nitrogen, phosphorus, sulfur, oxygen, halogen, silicon, and combinations 
thereof. Exemplary heteroatomic substituents contemplated herein are the 
following: 
##STR1## 
Specific examples of perfluoroalkyl-terminated lower aliphatic moieties 
useful herein include perfluoro-n-dodecylmethylene and 
perfluoro-n-octyl-t-butylene. 
iii. lower aliphatic-linked perfluoropolyethers having from about 6 to 
about 22 carbon atoms. The perfluoropolyethers contemplated herein are 
straight- or branched-chain perfluoroalkylene moieties having from 1 to 
about 5 carbon atoms, linked to form chains having a total of from about 6 
to about 22 carbon atoms by ether linkages (--O--). The aliphatic linking 
groups are lower aliphatic moieties as defined above. An exemplary 
perfluoropolyether moiety useful herein is the following: 
EQU HOCH.sub.2 CF.sub.2 O(CF.sub.2 O).sub.a (CF.sub.2 CF.sub.2 O).sub.b 
CF.sub.2 CH.sub.2 
wherein b is a number between 3 and 100, a is an integer greater than or 
equal to zero, a+b is no greater than 100, optionally no greater than 50, 
and the perfluoromethylene and perfluoroethylene moieties are randomly 
distributed in the chain. 
iv. perfluoroalkyl moieties as previously defined, having one fluorine atom 
of the terminal trifluoromethyl moiety replaced by hydrogen. An exemplary 
substituted perfluoroalkyl group is 11H-eicosafluorodecyl: 
EQU H--(--CF.sub.2 --).sub.10 -- 
Going back to the general structures of the present lubricants, A is a 
nucleus. A is selected from the group consisting of: 
i. substituted or unsubstituted, straight or branched, unsaturated lower 
aliphatic moieties as previously defined (except excluding saturated 
aliphatic moieties). 
An example of this category of nuclei is 2-butenyl: 
EQU --CH.sub.2 --CH.dbd.CH--CH.sub.2 -- 
ii. saturated and unsaturated cycloaliphatic having from about 4 to about 8 
ring carbon atoms. Examples of this category of nuclei include cyclobutane 
and cyclohexene. 
iii cycloaliphatic substituted by at least one moiety selected from the 
group consisting of heteroatoms as previously defined (as ring or non-ring 
substituents) and lower aliphatic as previously defined (including 
saturated lower aliphatic moieties). Exemplary moieties include those 
having the following structures: 
##STR2## 
and tetramethyltetrapropylenecyclotetrasiloxane. 
iv. arylene having from 1 to about 30 carbon atoms, including monocyclic 
and polycyclic rings, for example: 
##STR3## 
and naphthalene; 
v. arylene substituted by at least one moiety selected from the group 
consisting of lower aliphatic, cycloaliphatic, and heteroatoms, all as 
most broadly defined previously. The following are examples: 
##STR4## 
In the preceding formulas, M is a cation, for example, an alkali or 
alkaline earth metal. Specific metals contemplated as cations herein are 
potassium, sodium, and magnesium. Further examples of nuclei usable herein 
are those of porphyrin and cyclic sulfides. 
In the formula of the present compounds first set out above, each T 
represents at least one polar linking moiety. The purposes of the linking 
moieties are to provide strong orientation affinity to the aqueous phase 
during LB film deposition (as described below) and subsequently to anchor 
the lubricant to a substrate. 
Exemplary T moieties are selected from the group consisting of: 
##STR5## 
Where present in the foregoing formulas, R.sup.1 is selected from hydrogen 
and lower aliphatic, as most broadly defined above to include saturated as 
well as unsaturated moieties. Though not shown, an anion, for example 
halide or hydroxide, is associated with each quaternary nitrogen atom in 
the foregoing formulas. Linkages comprising chains of more than one of the 
polar linking moieties illustrated herein are also contemplated. 
Each Y of the general structures of the present compounds comprises a polar 
nonlinking moiety. (Nonlinking moieties are defined herein as those which 
do not directly or indirectly link a fluorocarbon moiety to a nucleus.) If 
more than one T group is present in the molecule, Y is an optional 
substituent herein. Y is preferably selected from the group consisting of: 
##STR6## 
In the foregoing formulas, M is a cation as previously defined, Z is 
halide, and R.sup.2 is selected from hydrogen and lower aliphatic as 
previously defined. 
R in the foregoing general structures is selected from saturated and 
unsaturated, substituted and unsubstituted, straight and branched lower 
aliphatic linkages having from 1 to about 5 carbon atoms. Examples of R 
linkages are: 
EQU --CH.sub.2 CH.sub.2 -- (ethylene); and 
EQU C(--CH.sub.2 --).sub.4 (neopentylene). 
In the general formulas first given above, n is at least one and the sum of 
n and m is at least two. Thus, each molecule has at least one polar 
linking moiety and a second polar moiety (which can be linking or 
nonlinking). There is no critical upper limit to the values of m, n, or 
their sum. Values of up to 18 (see Example 3 below) are illustrated herein 
for the sum of m plus n. 
Compounds as described herein may be made using any of a variety of 
synthetic methods. A preferred method contemplated herein, and illustrated 
in the examples, is to react 1) a fluorocarbon having a terminal 
functional group with 2) a precursor of the nucleus having one or 
(preferably) more functional groups. The reaction of the functional groups 
of the fluorocarbon and the precursor provides a polar linkage joining the 
two to form a compound according to the present invention. Thus, an X-T-A, 
X-T-R, or R-T-A moiety defined according to the general formulas herein 
can be created by carrying out a single reaction. 
For example, bis-nadic-anhydrybutene is a nucleus precursor having the 
following structure: 
##STR7## 
In the foregoing structure, the functional groups are two cyclic anhydride 
groups. One equivalent of bis-nadicanhydrybutene can be reacted with four 
equivalents of a hydroxy-terminated fluorocarbon, such as a fluoroalcohol 
having the following structure: 
EQU C.sub.12 F.sub.25 CH.sub.2 CH.sub.2 OH 
to form a compound according to the present invention having the following 
structure: 
##STR8## 
in which each X of the general formulas represents a C.sub.12 F.sub.25 -- 
terminal group, each T is an ester linkage, n is 4, A is: 
##STR9## 
and m is zero, so there is no Y present. 
Thus, one class of the present compounds can be prepared by reacting an 
anhydride or a corresponding free carboxylic acid, for example, any of the 
following: 
4,4'-(hexafluoroisopropylidene)diphthalic anhydride; 
3,3'4,4'-benzophenone tetracarboxylic dianhydride; 
pyromellitic dianhydride; 
1,2,3,4-cyclobutane tetracarboxylic dianhydride; 
4-sulfo-1,8-naphthalic anhydride potassium salt; 
2-sulfobenzoic acid cyclic anhydride; 
trimellitic anhydride chloride; 
4,5-dicarboxy-1,2,3-triazole; and 
bis-nadic-anhydrybutene 
with any of the following hydroxy-terminated fluorocarbons: 
[C.sub.8 F.sub.17 SO.sub.2 N(C.sub.2 H.sub.5)CH.sub.2 CH.sub.2 O].sub.2 
--P(O)OH; 
perfluoroalkyl hydroxyalkyl sulfamides, for example: C.sub.8 F.sub.17 
SO.sub.2 NH(CH.sub.2 CH.sub.2 OH); 
HOCH.sub.2 CF.sub.2 O(CF.sub.2 O).sub.n (CF.sub.2 CF.sub.2 O).sub.m 
CF.sub.2 CH.sub.2 OH; 
C.sub.8 F.sub.17 CH.sub.2 CH.sub.2 OH; and 
C.sub.12 F.sub.25 CH.sub.2 CH.sub.2 OH 
in an ordinary esterification reaction. Acid, anhydride, or other nucleus 
precursors can also react with a hydroxy-terminated fluorocarbon, such as 
tri(2-perfluoro-n-octyl)-ethyl citrate (TPFC): 
##STR10## 
in which s is 8 to form the present compounds. The triperfluoro-n-octyl 
citrate starting material illustrated above is not within the definition 
of the present novel compounds, but is contemplated to be useful per se as 
a lubricant herein. 
Another type of the present compounds can be prepared by reacting an imide 
or an amine functional group of a nucleus precursor with a carboxylic 
acid, alcohol, non-fluorine halide (i.e., chloride, bromide, or iodide), 
or non-fluorine acid halide functional group of a fluorocarbon. Exemplary 
imides are as follows: 
pyromellitic diimide; 
N-(2-hydroxyethylphthalimide; 
4,5-dichlorophthalimide; and 
N-2-bromoethylphthalimide. 
Exemplary amines and related materials are: 
bis(3,4-diaminophenyl)sulfone; melamine; 
2,4,6-triaminopyrimidine; 
6-thioanthine; and 
3,5-diamino-1,2,4-triazine. 
Exemplary halogen, acid halide, and carboxylic acid functional 
fluorocarbons for the above reaction are: 
perfluorododecyl iodide, CF.sub.3 (CF.sub.2).sub.11 I; 
perfluoro-1-octanesulfonyl fluoride; 
CF.sub.3 (CF.sub.2).sub.7 SO.sub.2 F; 
11H-Eicosafluorodecanoyl chloride, H(CF.sub.2).sub.10 COCl; 
C.sub.8 F.sub.17 CH.sub.2 CH.sub.2 I; 
C.sub.10 F.sub.21 CH.sub.2 CH.sub.2 I; 
C.sub.12 F.sub.25 CH.sub.2 CH.sub.2 I; 
perfluorodecanoic acid (PFDA), C.sub.9 F.sub.19 COOH; 
(C.sub.10 F.sub.21 CH.sub.2 CH.sub.2 S).sub.2 C(CH.sub.3)CH.sub.2 CH.sub.2 
CO.sub.2 H; and 
F[CF(CF.sub.3)CF.sub.2 O].sub.n CF(CF.sub.3)CO.sub.2 H, n=2-50. 
In addition, the fluoroalcohols previously listed, such as 
triperfluoro-n-octyl citrate, can also be converted to tosylates, which 
can then be reacted with the foregoing amines and imides. 
An example of the reaction products and novel lubricants derivable from the 
exemplary amines, imides and fluorocarbons is the perfluorododecyl iodide 
salt of bis(3,4-diaminophenyl)sulfone: 
##STR11## 
wherein each X is a perfluoro-n-dodecyl moiety. 
Another class of compounds according to the present invention is the 
reaction product of a chloride precursor of a nucleus with a fluorocarbon 
having a carboxylic acid or hydroxy functional group. For example, any of 
the following chlorides: 
phosphonitrilic chloride trimer (PNC); 
cyanuric chloride (CCl); or 
1,2-phenylene phosphorochloride; 
can be reacted with any of the carboxylic acid or hydroxy functional 
fluorocarbons described above. For example, PNC can be reacted with TPFC 
or CCl can be reacted with PFDA. 
The chlorides previously described can also be reacted with 
perfluorosulfonyl alkyl amides as previously described (which are the 
reaction products of fluorocarboxylic acids and alkylsulfonamides). For 
example, the reaction product of phosphonitrilic chloride trimer with 
perfluoro-n-octyl-2-hydroxyethylsulfonamide has the following structure: 
##STR12## 
wherein X is a perfluoro-n-octyl moiety. 
Another class of useful nucleus precursors is a diisocyanate or a 
polyisocyanate terminated precursor, which can react with a carboxylic 
acid, hydroxy, or amine functional group of a fluorocarbon to yield an 
carbamate linkage. An exemplary diisocyanate nucleus precursor 
contemplated herein is diphenylmethane-4,4'-diisocyanate. 
Acrylates are another class of nucleus precursors useful herein,. Exemplary 
acrylates have the following structures: 
2-hydroxyethyl acrylate, CH.sub.2 .dbd.CHCOOCH.sub.2 CH.sub.2 OH; 
pentaerythritol triacrylate (PETA), 
(CH.sub.2 .dbd.CHCOOCH.sub.2).sub.3 CCH.sub.2 OH; 
2-isocyanatoethyl methacrylate, 
CH.sub.2 .dbd.C(CH.sub.3)COOCH.sub.2 CH.sub.2 NCO); and 
glycidyl methacrylate, CH.sub.2 .dbd.C(CH.sub.3) 
##STR13## 
An example of the novel lubricants derivable from the reaction of acrylates 
and fluorocarbons is an ester of [C.sub.8 F.sub.17 SO.sub.2 N(C.sub.2 
H.sub.5)CH.sub.2 CH.sub.2 O].sub.2 --P(O)OH and PETA. The resulting 
product has the following formula: 
EQU (CH.sub.2 .dbd.CHCOOCH.sub.2).sub.3 CCH.sub.2 O--P(O)[OCH.sub.2 CH.sub.2 
N(C.sub.2 H.sub.5)SO.sub.2 C.sub.8 F.sub.17 ].sub.2 
This lubricant can be further cross-linked through its three acrylates to 
form a mechanically strong film. The structure immediately above fits into 
the general structural formula: 
EQU (X--T).sub.n --R(T--A).sub.n 
as follows. X is perfluoro-n-octyl; the n associated with X is two; the T 
associated with X is: 
EQU [OCH.sub.2 CH.sub.2 N(C.sub.2 H.sub.5)SO.sub.2 ] 
(which is a chain of three polar groups as previously identified); the n 
associated with X is two, R is: 
##STR14## 
each of the T's associated with each A is an ester linkage, A is CH.sub.2 
.dbd.CH--, and the n associated with A is 3. This formula thus illustrates 
that each T can be a string of polar groups as individually identified 
previously, within the scope of the present invention. 
LUBRICATED MAGNETIC MEDIUM 
Another aspect of the invention is a lubricated magnetic medium comprising 
a planar, polar surface of the medium covered with a monolayer comprising 
a compound having the structure described in the preceding description, 
except that A can also be a saturated lower aliphatic group in this 
embodiment of the invention. 
The monolayer may be a Langmuir-Blodgett (LB) monolayer less than 120, 
preferably less than 70, most preferably less than 30 Angstroms thick. The 
monolayer may also be applied to the substrate in another manner. A 
background on the nature and formation of LB films and the amphiphilic 
materials capable of forming LB films is provided in Agarwal, 
"Langmuir-Blodgett Films," Physics Today, Jun., 1988. "Amphiphilic" is 
also defined in this reference. The definition of "amphiphilic" and the 
description of LB films in the Agarwal reference are hereby incorporated 
herein by reference. 
Generally speaking, an LB film is a tightly packed single layer of 
amphiphilic molecules oriented with their hydrophilic ends (here, the two 
or more T and Y moieties) adjacent to the substrate and their hydrophobic 
ends (here, the X moieties) standing above the substrate. 
While the novelty or scope of the invention does not depend on the accuracy 
of this theory, it is contemplated that the compounds of the present 
invention provide superior, durable lubrication because the T and Y 
moieties of the present compounds, as well as any polar moieties included 
in the structure of A and R, are bonded securely to the polar surface of 
the magnetic medium by Van der Waals forces between the free electron 
pairs of the polar moieties and oxygen atoms present in the magnetic 
medium. (A typical thin-film magnetic medium has either a metal oxide 
surface or a carbon surface which oxidizes due to its exposure to air.) 
Dipole interactions and ionic or electrostatic attraction also contribute 
to bonding. 
For the preferred compounds in which A is a planar and aromatic 
heterocyclic ring, the ring will interact with the pi-electrons of an 
amorphous carbon magnetic recording disk protective coating. Additionally, 
the amine salts will interact with and form strong bonds with a 
spontaneously oxidized carbon surface. 
Because of these bonds between each lubricant molecule and the substrate, 
the A and R moieties associated with the polar groups are closely packed 
(due to Van der Waals attractive forces between the polar moieties of 
adjacent molecules), and are fixed substantially in a lubricant plane 
parallel to the polar surface of the magnetic medium. The X moieties, 
which are very nonpolar, extend substantially perpendicularly above the 
lubricant plane, which is how they are oriented when an LB film of the 
lubricant is applied to the magnetic medium. Since each fluorocarbon 
moiety is linked to the nucleus by a polar linking group, the base of each 
fluorocarbon chain is anchored to the substrate. 
The several fluorocarbon moieties of a lubricant are preferably identical, 
are each anchored at one end in identical fashion, and extend 
perpendicularly upward from the substrate. The fluorocarbon chains are 
zig-zag chains, as dictated by their tetrahedral bond geometry. This 
symmetrical arrangement means that the corresponding atoms of each 
fluorocarbon chain are disposed the same distance above the substrate, so 
the fluorocarbon chains have a tendency to nest, allowing close packing of 
the chains. 
The nuclei of the monolayer are tightly packed and the X moieties are 
numerous and preferably identical, so the X moieties stand like blades of 
grass above the substrate, providing a dense, durable lubricating layer 
which interfaces with a scanning read/write head to reduce friction. 
This theory is illustrated in FIGS. 1 and 2. FIG. 1 schematically shows a 
section of the substrate 10 covered by an array of closely packed 
rectangular "tiles" such as 12, each representing the nucleus A and the 
four polar linking groups T of the following molecule illustrated above: 
##STR15## 
At the intersecting corners such as 14, 16, 18, and 20 of four adjacent 
molecules, Van der Waals forces cause the T moieties to be mutually 
attracted, and each T is anchored to the substrate 10 because it tends to 
rotate around its single bond with the nucleus A until its carbonyl moiety 
is oriented in a position of maximum attraction to the substrate below 
(with the carbonyl double bond parallel to the lubricant plane). 
Many X fluorocarbon chains--there is one X chain per T linking group--are 
omitted from FIG. 1 to more clearly illustrate the lubricant plane defined 
by the molecules such as 12. Since the four T moieties of the intersecting 
corners such as 14-20 of adjacent molecules are closely packed, the 
fluorocarbon moieties associated with each linking group are equally 
closely packed at their bases. 
Referring to FIG. 2, two of the four X moieties of a set of intersecting 
corners (such as 14-20) are shown from the side. The fluorocarbon chains 
22 and 24 are identical, and thus are capable of nesting because their 
respective backbone atoms line up, much like the crystalline structure of 
an oriented polyolefin film. This arrangement allows many fluorocarbon 
chains to be disposed perpendicular to the lubricant plane defined by the 
molecules such as 12. 
The lubricants described herein are applied in essentially conventional 
fashion to thin-film magnetic media, for example, using the LB coating 
technique. While only one Z-type monolayer of the present lubricants can 
bond directly to the substrate, more than one Z-type layer (with the 
fluorocarbon chains extending away from the substrate, as shown in the 
figures) can be built up by the LB film formation method. This may be done 
to ensure complete coverage of the substrate by a monolayer, particularly 
if the substrate surface is uneven. The present lubricant layers can also 
be overcoated with another lubricant, for example a fluorocarbon oil which 
is compatible with the fluorocarbon chains of the LB monolayer. 
Before applying a LB monolayer of the present lubricants, it is important 
to thoroughly clean the magnetic medium surface, as by immersion in a 
solvent such as isopropanol followed by rinses of deionized water, until 
the surface to be coated has a high electrical resistance (for example, 
about 18 megohms per square). 
EXAMPLES 
The following working examples provide further exemplification of the broad 
scope of the present invention, and enable one of ordinary skill in the 
art to carry out the present invention. 
EXAMPLE 1 
Triaminopyrimidine salts of perfluoropolyether acid, with three long chain 
perfluorocarbons moieties on a nitrogen heterocyclic ring, were prepared 
as follows: 
0.4 g of 2,4,6-triaminopyrimidine (F.W.125.14) was dissolved in 5 ml of 
deionized (DI) water and added, with stirring, to a solution of 40 g of an 
acid of formula 
##STR16## 
having an average molecular weight of 4000 in a FREON 113 solvent (50 ml). 
(FREON is a trademark of E. I. DuPont de Nemours & Co., Wilmington, Del. 
for chlorofluorocarbons.) The solution turned milky immediately and 
appeared to thicken. After 2 hours of continuous stirring the two phases 
were separated and the solvent of the organic phase was removed by 
evaporation. 39 g of amber colored oily material were recovered. Infrared 
spectral bands, including a series of bands centered about 3450, 3350 and 
3180 cm.sup.-1 (.nu.N-H in varying degrees of association), 1690 cm.sup.-1 
(.nu.C=O of CO.sub.2 --NH.sub.3 and a red shift of about 190 cm.sup.-1 
from that of the fluorinated acid) and 1300, 1240, 1180 cm.sup.-1 
(.nu.CF.sub.2 rCF.sub.2); also bands near 1610, 980 and 780 cm.sup.-1 
(attributable to the heterocyclic ring) of the oily material were 
observed. 
These spectral characteristics are consistent with the following structure: 
##STR17## 
wherein C.sub.4 N.sub.2 is: 
##STR18## 
EXAMPLE 2 
Thiourea salts of perfluoropolyether acid moieties, containing two long 
chain perfluoropolyether moieties on a polar thiourea base, are prepared 
as follows: 
0.4 g of thiourea are dissolved in 10 ml of deionized water. 40 g of an 
acid of the formula: 
##STR19## 
is dissolved in 50 ml of FREON 113, added to the thiourea solution with 
stirring, and heated for 2 hours. The two phases are separated; the lower 
organic phase is washed with deionized water, then the solvent is 
evaporated. A light colored liquid is obtained. The IR spectrum includes 
absorption bands near 3600 CM-1 (.nu.N-H, broad), 1820 cm-1 (.nu.C.dbd.S), 
1670 cm-1 (.nu.C.dbd.O of --CO.sub.2 NH.sub.3), 1280, 1240, and 1180 cm-1 
due to --CF.sub.2, also 1030, 860 and 800 cm-1, among others, due to the 
perfluoropolyether acid. These spectral characteristics are consistent 
with the following structure: 
##STR20## 
Other exemplary amines are melamine and tetrakis(3-aminopropyl) 
tetramethyl cyclotetrasiloxane. Other exemplary fluorocarbons are 
perfluorododecyl iodide and fluoroalkylsulfonic and fluoroalkylphosphoric 
acids such as DuPont's Zonyl TBS and UR materials. 
EXAMPLE 3 
The condensation product of phosphonitrilic chloride and a 
trifluoroalkylcitrate was prepared. The product contained 18 fluorocarbon 
chains on a phosphorus and nitrogen aromatic heterocyclic ring. 
1.1 g of phosphonitrilic chloride trimer (P.sub.3 N.sub.3 Cl.sub.6) having 
the following nuclear formula: 
##STR21## 
was dissolved in chloroform (25 ml), then was added dropwise to 11.4 g of 
a trifluoroalkyl citrate having this structure: 
##STR22## 
(mw .about.1600, n is 6, 8, 10, 12, or 14, mostly 8 or 10), in FREON 112 
(50 ml) and triethylamine (10 ml) while stirring and heating. Refluxed 
overnight, 10 g of light amber material were recovered. Major IR bands 
were observed near 2960 cm-1 (.nu.CH.sub.2), 1750 cm-1 (.nu.CH.sub.2), 
1750 cm-1 (.nu.C.dbd.O, --CO.sub.2), 1200 cm-1 (CF.sub.2, CF.sub.3 broad), 
and 1040 cm-1 (possibly P--O--C). This spectrum is consistent with six 
terminal groups having the following structure: 
##STR23## 
on the following nucleus: 
##STR24## 
The IR absorption bands due to phosphonitrilic chloride near 1240 cm-1 
(main) and 1300, 1190, 1140 and 980 cm-1 (minor) were masked by the 
absorption bands of the CF.sub.2 and CF.sub.3 fluoroalkyls. 
EXAMPLE 4 
Perfluoropolyether amines of triaminopyrimidine and 3 long chain 
perfluoropolyethers were formed as follows: 20 g of a diol of the formula: 
EQU HOCH.sub.2 CF.sub.2 O(CF.sub.2 O).sub.a (CF.sub.2 CF.sub.2 O).sub.b 
CF.sub.2 CH.sub.2 OH 
having a molecular weight of about 4000, FREON 122 (25 ml), and 5 ml of 
triethylamine were mixed Then a xylene solution of tosyl chloride (1.9 g 
in 25 ml) was added and the mixture was stirred for 2 hours. Then an 
aqueous of triaminopyrimidine, (NH.sub.2).sub.3 C.sub.4 N.sub.2, 
containing 0.4 g of LiOH (0.4 g/10 ml) was added. After refluxing 
overnight 20 g of a light viscous liquid were obtained. Its significant IR 
bands included 3500 cm.sup.-1 (--NH--), 2950 cm.sup.-1 (CH.sub.2), 1600 
cm.sup.-1 (heterocyclic), 1200-1100 cm.sup.-1 (CF.sub.2). These bands are 
consistent with the following structure: 
EQU [HOCH.sub.2 CF.sub.2 O(CF.sub.2 O).sub.a (CF.sub.2 CF.sub.2 O).sub.b 
CF.sub.2 CH.sub.2 NH].sub.3 T 
wherein T has the following structure: 
##STR25##