Surface rearrangement of tailored polyurethane-based coatings.

Polyurethane coatings with different network composition were prepared from an oligomeric diol, a diisocyanate, and a low molecular weight triol. The glass transition temperature of the network was tuned by the ratio of diol and triol and the composition (aromatic or aliphatic) of the diisocyanate. All coatings were studied for their bulk properties as well as their surface properties. It was found that by the addition of a fluorinated additive the surface free energy of the coating was lowered by approximately 15 mN * [m.sup.-1], leaving the bulk properties intact. It was also shown that these polyurethane coatings are able to adapt their surface free energy in a reversible manner when exposed to water. The magnitude and rate of surface rearrangement is strongly dependent on the network density of the coating.

Keywords: Differential scanning calorimetry, FTIR, ATR, hardness, scratch resistance, surface energy, fluorinated polymers, polyurethane, smart coating

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The precise structural and morphological control of organic surfaces is of increasing interest in basic and applied research. (1,2) Surfaces of polymer solids are decidedly different from those of more rigid materials such as metals and ceramics. Polymer molecules have much greater freedom for rearrangement; therefore, they may orient themselves differently at the surface than in the bulk. Accordingly, the surface properties of a polymer solid may not be the same as the properties of the solid in the bulk.

It is generally acknowledged that polymers are sufficiently mobile on the molecular scale to reorganize molecularly at the surface in a relatively short time in relation with the environment. (3-11) The interface between a polymer and the surrounding medium will rearrange itself in order to get a minimum interfacial free energy. Phenomena that might be related to this aspect of polymer surfaces were recognized in the early 1960s by studies on hydrogels. The contact angles of water on these gels, which contained as much as 98% water, were higher than expected (it was expected that the gel was completely wetted by the water). (12)

It is known that polymer surfaces undergo a rearrangement when the environment is changed, i.e., the tendency is the exposure of hydrophobic moieties to a hydrophobic environment (such as air) and hydrophilic moieties to a hydrophilic environment (such as water). Therefore, it seems possible to modify the surface properties by incorporating active components, i.e., hydrophilic or hydrophobic, in the bulk material surface.

The understanding and control of the structure and mobility at the polymer surface are of interest in different areas such as biocompatibility, antifouling paints, rubbing improvement, wear, wetting, and adhesion.

The scope of this article is to investigate the rearrangement of the surface upon change of the environment as a function of the network density of the polymer network, and to study the effect of the addition of fluorinated components on this rearrangement.

Fluorinated polymers have demonstrated many properties that are desirable in coatings, for example, excellent hydrophobicity and oleophobicity, excellent chemical resistance, and good weatherability. (13-17)

Copolymers containing highly fluorinated side chains are reported to be highly hydrophobic materials when in contact with air (7, 18, 19); a block copolymer segregates to the surface, driven by the low surface energy of the fluorinated blocks. However, the main drawback of this approach is an alteration of the bulk properties due to the high fluorine content in the block copolymer. The coating properties of interest are basically surface properties, which make the presence of fluorine in the bulk unnecessary. Migration of fluorinated components in coatings was already proven in self-stratifying coatings. (20-23)

In our study we focus on polyurethane (PU) based coatings because of their highly versatile applications in combination with their excellent bulk properties. In many of the applications where the excellent mechanical properties of polyurethanes are required, it is expected that surface modification does not affect the bulk properties. Wesslen et al. (5,24,25) have shown that the addition of small amounts (5 wt%) of an amphiphilic polymer in polyurethanes and polyurethane ureas is sufficient enough to give the material an amphiphilic nature with unaltered bulk properties. In the same way, using 5 wt% of hydrophobic polymers as additives, Santerre et al. (26) reported modified PU surfaces with wettability features equivalent to polytetrafluoroethylene (PTFE), with no detectable additive effects on the bulk structures. We could, therefore, expect that reactive additives incorporated in small amounts during synthesis would lead to the surface modification of PU networks without changing the bulk properties of the material.

[FIGURE 1 OMITTED]

This study pursues a double goal: (a) to synthesize and characterize polyurethane networks with a low surface energy; and (b) to investigate the rearrangement of the surface upon immersion of the coatings in water.

EXPERIMENTAL SECTION

Materials

Polyols (difunctional D, trifunctional T) and isocyanates (I) were obtained from the manufacturers and were used as received (see Table 1).

The tetrahydrofuran (THF) that was used as a solvent during the synthesis was of HPLC grade. Its purity was more than 99.7% and did not contain any stabilizer (stabilizers that are commonly used are alcohols, which can react as additives in the PU network).

Synthesis

In this study, the network density was tuned by changing the ratio [diol/triol] while keeping the network chemistry unchanged. Besides variation in [diol/triol] the molecular weight (chain length) of the components was also changed. Basic PU networks (without additives) were synthesized using a three-step method. First, 50 g of diol (D-1 or D-2) was dried in the reactor under vacuum at 80[degrees]C for one hour. In the first step, the isocyanate (I-1 or I-2) was reacted with the polyol. This reaction was carried out in a glass reactor for four hours, at 80[degrees]C (thermostated bath), under stirring and vacuum. In the second step, the reactor was brought back to room temperature and pressure; the crosslinker (T-1 or T-2) dissolved in dry THF was added to the prepolymer. The mixture, containing 50 wt% of reactants, was stirred until complete dissolution was attained. After sample preparation, i.e., coating aluminum or glass panels using a Doctor blade, crosslinking was completed in an oven at 110[degrees]C for 16 hr. The coated panels were allowed to cool to room temperature in the oven and were subjected to surface analysis such as FTIR and determination of the surface energy.

The effect of a fluorinated additive on the properties of the coatings was studied on systems composed of the same ingredients. By the addition of the fluorinated alcohol to the diol before the first step of the polyurethane synthesis, the network was changed due to the addition of a monofunctional "chain-stopper." In Figure 1, a schematic representation of the network formation with and without using the fluorinated additive is given.

Characterization

DIFFERENTIAL SCANNING CALORIMETRY (DSC): Glass transition temperatures were determined on the cured coatings. Approximately 15 mg of coating was heated from -100[degrees]C to 100[degrees]C at a heating rate of 10[degrees]C * min[.sup.-1] using a DSC2920 from TA Instruments. A cooling and a second heating step followed the first heating step. To avoid aging phenomena, the glass transition temperature was determined on the second heating curve.

For the glassy networks, the determination of the glass transition temperature seemed to be difficult using the standard procedure, so for these systems a temperature-modulated DSC (TMDSC, DSC2920, TA Instruments) was used. In these experiments the samples were heated from -25[degrees]C to 200[degrees]C at a heating rate of 3[degrees]C * min[.sup.-1]. During the heating scan the temperature was modulated with 1.5[degrees]C * min[.sup.-1].

SURFACE ENERGY DETERMINATION: The surface energy of the coatings was determined using a Kruss G10 goniometer interfaced to image capture software. Contact angles were determined from sessile drops (approx. 2 [micro]l) of water (Millipore grade) and diiodomethane (Aldrich, 99%). The contact angle was determined during the first 10 sec after application of the droplet. The measured contact angle between the drop and the surface and the surface tensions of the test liquids were used to calculate the surface energy by the method of Owens and Wendt. (27)

HARDNESS AND ELASTIC MODULUS: A Fischerscope H100C microindenter that senses both load and displacement was used to measure the hardness and elastic modulus on cured coatings. The applied load on a Vickers indenter was increased instantaneously to 1 mN for 10 sec, and then the load was decreased.

INFRARED SPECTROSCOPY (FTIR): Some coatings were characterized using infrared spectroscopy. The spectra were recorded on a Biorad spectrometer equipped with a diamond ATR crystal. Scans were collected with a resolution of 2 c[m.sup.-1] from 4000 to 500 c[m.sup.-1].

[FIGURE 2 OMITTED]

RESULTS AND DISCUSSION

Unmodified Elastomeric Networks

From the formulations without the fluorinated additive, some insight into structure-property relations was obtained. For four different formulations, the coatings were characterized on surface hardness, elastic modulus, glass transition temperature, and surface energy. In the different formulations the ratio of difunctional polyol and trifunctional polyol was varied, as well as the molecular weight of the diol to change the network density of the cured polyurethane (see Table 2).

Before performing the synthesis, the effect of network composition was estimated using the group contribution theory of van Krevelen. (28) According to this theory, the effect of chemical composition can be reflected in the properties of the resulting material. The average molecular weight between crosslinks ([M.sub.c]) was set by the ratio of diol and triol and the molecular weight of the components (see Table 2). Based on the additive group contributions, it is expected that the resulting coatings will have a glass transition temperature ([T.sub.g]) of approximately -30[degrees]C. Figure 2 shows the results of the calculated and experimental values of the [T.sub.g].

[FIGURE 3 OMITTED]

The values of the [T.sub.g] of the polyurethanes all showed a broad transition at low temperatures. All thermograms showed no other transition than the [T.sub.g], indicating the completeness of the reaction and the absence of remaining solvents.

Comparison of the predicted values of [T.sub.g] and the experimental values showed that there was a good agreement. However, there was some deviation for the higher molecular weight diol used (coating 1). This deviation was probably due to the relatively high viscosity of the reaction medium. As a consequence, incomplete conversion and incorporation of network defects are the basis for deviation from the theoretical values that were calculated.

The coatings are truly elastomeric, as reflected by the values of the hardness and moduli which were determined by indentation experiments. All these systems exhibited a modulus of approximately 15 MPa, which is acceptable for polyurethane elastomers. (29) All these materials were well above their [T.sub.g] during measurement and extreme differences were not observed when indentation properties were plotted as a function of the crosslink density.

All coatings were subjected to surface energy analysis. During the determination of the surface energy of these networks, it was observed that the time at which the surface energy was determined is of importance; the surface of the coatings changed upon exposure to moisture. The results that are reported were all determined immediately after removing the coated panels from the oven that was cooled to room temperature. Figure 3 shows the contact angles of the wetting liquids used for analysis as a function of the crosslink density.

As can be seen, the main differences were observed in the contact angles of water. Higher crosslink density is connected with larger contact angles of water. The contact angle of diiodomethane remained almost unaffected. This is also reflected in the values of the surface energy of the coatings. The values of the contact angles, as well as the dispersive and polar parts of the surface energy, are given in Table 3.

From these results it can be seen that the dispersive part of the surface energy dominates over the polar part, indicating the hydrophobic character of the polyurethane network.

Modified Glassy and Elastomeric Networks

Based on the knowledge that coating properties can be tuned by coating composition, we decided to prepare two different series of fluorinated coatings: one series based on T-1 and I-1 that results in "elastomeric" coatings, and a second series based on T-2 and I-2 that results in "glassy" coatings. These two series were designed on the basis of additive group contributions to material properties (28) (Table 4).

The coatings that were prepared from these formulations were applied on glass and characterized on surface energy, hardness, and glass transition.

The elastomeric and glassy polyurethane networks were designed to exhibit clear differences in [T.sub.g], based on the additive group contributions. The results, shown in Figure 4, are a clear indication that the theory of van Krevelen is applicable to tune the properties of the coatings. The rigid diisocyanate (TDI, I-2) in combination with the low molecular weight triol (TMP, T-2) results in a more rigid, glassy type of polyurethane.

It can be observed (Figure 4) that the effect of the fluorinated additive on the [T.sub.g] of the rubbery networks is negligible. This was also observed by Game et al. (29) for polyurethane networks containing approximately 1 wt% fluorinated additive.

As can be expected, the fluorinated additive had a large effect on the surface energy of the coatings obtained. The average value of the surface tension dropped drastically from approximately 26 mN * [m.sup.-1] for the elastomeric polyurethane coatings (coatings 1-4) to about 11 mN * [m.sup.-1] for the fluorinated analogue (coatings 11-14). Based on the network composition, the ratio of the polar-to-disperse part of the surface energy was changed (see Table 5), as well as the response of the network in contact with water. This will be discussed in the upcoming section on the responsive effect of the polyurethane coatings.

[FIGURE 4 OMITTED]

From Tables 1 and 5 it can be seen that the dispersive part of the surface energy dropped drastically from about 24 mN * [m.sup.-1] for coatings 1-4 to about 9.5 mN * [m.sup.-1] for the fluorinated elastomeric networks (coatings 11-14). According to literature, (30-34) the dispersive parts of fluorinated systems vary from 14 mN * [m.sup.-1] for C[F.sub.2]-rich materials (PTFE) to 7 mN * [m.sup.-1] for C[F.sub.3]-rich materials. These data were reported on materials well above their [T.sub.g]. In our case, those values for the dispersive part of the surface energy were close to the values of the C[F.sub.3]-rich reports.

When these results were plotted as a function of the-NHCO content in the coatings, Figure 5 was obtained.

It can be seen that the polar part of the surface tension is linearly dependent on the NHCO content of the network, the dispersive part of the surface tension shows a different behavior for the elastomeric ([??] *) and glassy ([square] [black square]) networks. The behavior of these coatings on water immersion, to be discussed in the upcoming section, is explained by this phenomenon/behavior.

The mechanical properties of the coatings, i.e., the modulus and indentation hardness, show clear differences with respect to the glassy and elastomeric networks. Especially for the glassy networks, the hardness and modulus show a linear relation with the crosslinks in the coatings (Figure 6), while for the elastomeric networks the crosslink density has merely a minor effect on indentation properties.

[FIGURE 5 OMITTED]

Effect of the Length of the F-Sidechain

The effect of the length of the fluorinated sidechain was studied on the glassy coating formulations (Table 6). The coatings were all evaluated on surface tension and indentation properties.

For both coatings, the hardness (HM) and modulus (E) increased with increasing crosslink content (see Table 7). For surface tension, the polar and dispersive parts are important.

The first observation that we can make is that as soon as fluorine was introduced in the coatings, the surface free energy dropped drastically (from about 38 mN * [m.sup.-1] to approximately 12 mN * [m.sup.-1]). The coatings remained hydrophobic, i.e., the surface energy was mainly due to dispersive interaction. Furthermore, it can be seen that both the polar and dispersive parts of the surface energy were reduced upon introduction of the fluorinated additive.

The influence of the length of the pendent fluorocarbon moiety is evident; an increased chain length results in a lower surface energy. However, as the length of the fluorinated additive increased, the average surface roughness of the coatings also increased, as observed for the fluorine containing coatings.

When crosslink density is taken into account it might be stated that the flexibility plays a role in the surface energy. The higher the crosslink density, the lower the surface energy. This observation is supported by results published by Tsibouklis et al. (35)

[FIGURE 6 OMITTED]

Response of the Fluorinated Coatings Upon Immersion in Water

During the analysis of the polyurethane coatings, the response of different networks on water was found. In this section, this response is analyzed in more detail. From immersion experiments in water, it was observed that the surface energy of the fluorinated networks during exposure eventually matched the value of the nonfluorinated networks upon immersion in water. The results are presented in Figure 7.

By the use of ATR-FTIR spectrometry experiments, the change in composition of the polyurethanes was studied. As a typical example, the spectra of a dry and water-immersed polyurethane coating is shown in Figure 8. From these, it was learned that, upon immersion, the composition of the surface of the immersed coating changed with respect to the ability to form hydrogen bonds. This can be clearly seen in the change of the peak of the amine (3400 c[m.sup.-1]), and the change of the peak of the carbonyl (1730 c[m.sup.-1], which shows a second peak for hydrogen bonded carbonyl groups at 1695 c[m.sup.-1] in the water-immersed coating. Besides these large and obvious changes there are also some minor changes that might be of use in elucidating the mobile segments in the polyurethane.

[FIGURE 7 OMITTED]

The chemical structure of the polyurethane indicates that the increase of the polar component of the surface free energy can be a result of the exposure to water of the -C-O-C- groups of the polyol and/or the -NHCO-groups. When using angle dependent FTIR-ATR spectroscopy, a variation in analysis depth is obtained. The penetration depth is dependent on both wavelength and incident angle, and by using an incident angle of 40[degrees] the penetration depth is four times the penetration depth using an angle of 60[degrees]. The results of the spectra at different angles are shown in Figure 9.

It can be seen that at the surface of the coating (approximately 2 nm, spectrum at 60[degrees]) the composition is slightly different than at a depth of approximately 8 nm (spectrum at 40[degrees]). The peaks of the carbonyl groups at approximately 1700 c[m.sup.-1] can be attributed to hydrogen-bonded carbonyl (1695 c[m.sup.-1]) and "free" carbonyl groups (1730 c[m.sup.-1]). As expected, at the surface more hydrogen-bonded carbonyl groups are present, which is reflected in the ratio of the 1695 to 1730 c[m.sup.-1] intensity. The ether linkages in the polyurethane coatings, present at 1100 and 1150 c[m.sup.-1], also show some differences with depth. Based on these observations, it is expected that both the -NHCO- and -C-O-C- groups migrate to the surface upon immersion in water. (36)

[FIGURE 8 OMITTED]

As was observed during the analysis of the polyurethane coatings on surface energy, the glassy and elastomeric coatings showed a different response. The comparison of a rigid (glassy) and elastomeric (rubbery) network is given in Figure 10. It is worth noting that the surface free energy, after 360 min of immersion, reach asymptotic values when plotted against immersion time. The elastomeric system ([black square]) reaches a surface tension of approximately 40 mN * [m.sup.-1] and a glassy system (*) exhibits a surface tension of 20 mN * [m.sup.-1] after immersion in water.

The differences that were observed for the different coatings are probably a result of the network density. The higher the network density, the lower the mobility. The network mobility plays an important role in the molecular reorientation when in contact with a high surface tension liquid such as water. Models for molecular mobility at the surface are shown in Figure 11. In this figure, a schematic representation is given for the fluorine tails in mobile and rigid networks.

Model (A) represents a polymer backbone with the fluorinated tails attached to the main chain. This backbone has free rotation (represented by the arrow) along the axis of the polymer backbone. Model (B) represents a polymer backbone, with the fluorinated tails attached to the main chain, that contains rigid building blocks (without free rotation). Model (C) represents a crosslinked macromolecule which is (partially) crosslinked and where there is still some rotational mobility left due to network imperfections. Model (D) represents a polymer network with a high degree of crosslinking. Because of this high degree of crosslinking, no rotation of fluorinated tails is possible.

The lower network mobility in the glassy polyurethane network does not allow a fast reorientation (see Figure 10 *). The fluorinated chains that remain at the surface hide the high energy groups. When we take a look at the dispersive part of the surface energies that were determined, we see that in all cases this dispersive part of the surface energy increases and that the dispersive part of the surface energy determines the total surface free energy (Table 8).

[FIGURE 9 OMITTED]

The glass transition temperatures of the glassy and elastomeric networks differ approximately 50[degrees]C; consequently, the segmental mobility of the matrix is much lower in the glassy network than for the elastomeric network at room temperature, and reorientation of the amphiphilic polymer or segments would be a very slow process.

The effect of rotational mobility on the hydrophilicity of the polymer-air-interface is clearly evident in the observed contact angles of water. In the glassy coating it is expected that free rotation along the axis of the polymer chain is not allowed, as a result of the aromatic ring structure of the 1-2.

Indentation experiments on some coatings before and after water immersion showed that the hardness of the elastomeric networks remained almost constant, whereas the glassy networks showed slightly decreased indentation hardness.

The main driving force for the rotation of the molecules at the surface is the strong interaction between water and the hydrophilic groups of the macromolecule (minimizing the interfacial tension). Because of this and the mobility of the network, networks with high mobility show a larger adaptive power than networks with lower mobility. For the fluorinated systems the contact angles for water will remain high for the glassy systems, whereas the contact angles for water will decrease when an elastomeric coating is exposed to water by the rearrangement of the fluorinated groups into the bulk.

[FIGURE 10 OMITTED]

[FIGURE 11 OMITTED]

To check whether the observed phenomena were the dissolution of certain compounds, we performed a Soxhlett extraction, using hexane on the coatings, and then repeated the immersion experiment. The results showed that there was no significant difference in surface free energy, indicating a covalent bonding of the fluorinated additive into the polyurethane network. The values of the contact angles changed slightly in such a way that the polar part of the surface energy decreased while the dispersive part of the surface energy increased. From the work of Chen and Ruckenstein, (37) it was learned that the medium of contact (polar or apolar, aromatic or aliphatic) could have a dramatic effect on the surface arrangement of functional groups and the resulting surface energy or interfacial tension when in contact with the medium.

Reversible Response

Thus, the response of the polyurethane networks was present in both the modified and unmodified networks, and the responsive effect had nothing to do with dissolution of active components in the surrounding medium. If this phenomenon of burying or exposure of certain groups occurs according to the rotational mobility, as represented in Figure 11a and 11c, a reversal process should also occur when the water is removed and the surrounding phase is changed from water to air.

[FIGURE 12 OMITTED]

The reversible nature of the environmental-induced surface rearrangement process is demonstrated by monitoring the surface energy as a function of "recovery-time" (see Figure 12), which is defined as the time after exposure to the atmosphere at room temperature, following immersion in water.

In the given figure, it can be seen that the surface free energy of the coating before water immersion agrees well with the surface free energy measured after being recovered and "dried." This almost complete recovery was found for the coatings with low network density, while for the high network density recovery is not yet reached after six hours of recovery.

CONCLUSIONS

In this study it was found that tailoring the properties of polyurethane-based coatings is possible by choosing the ingredients of the coating formulation. By choosing different molar ratios of diol and triol, in combination with an aromatic or aliphatic diisocyanate, the glass transition of the coating was tuned. The surface free energy of the coating can also be tuned by the formulation, i.e., the addition of a fluorinated additive. The bulk properties of the coating remained unchanged upon addition of the fluorinated additive.

The polyurethane networks undergo a reversible physical rearrangement in a polar environment, such as water, by exposing the more polar moieties of the molecular chains. This rearrangement takes place in order to lower the interfacial energy of the system. The rearrangements occur to depths greater than 8 nm from the surface. The network density (reflected in [T.sub.g] values) has a large effect on the rearrangement in water. This is directly related to the mobility differences of the molecular chains of the polyurethanes.

Table 1 -- Overview of the Main Components of the Polyurethane Networks

Code  Name                                               Supplier

D-1   CAPA 2100A                                         Solvay
D-2   CAPA 2054                                          Solvay
T-1   CAPA 3050                                          Solvay
T-2   1, 1, 1-tris(hydroxymethyl)propane (TMP)           Aldrich
I-1   1, 6-hexane-diisocyanate (HDI)                     Aldrich
I-2   toluene-2,4 diisocyanate (TDI)                     Aldrich
F-1   1H, 1H, 2H, 2H-perfluorooctan-1-ol, FLUOWET EA600  Clariant
F-2   1H, 1H, 2H, 2H-perfluorodecan-1-ol, FLUOWET EA800  Clariant
F-3   1H, 1H, 2H, 2H-perfluorododecan-1-ol,              Interchim

      Molecular Weight  OH Value
Code  g * mol[.sup.-1]  mg KOH * [g.sup.-1]

D-1   1000              112
D-2    550              204
T-1    540              310
T-2    134
I-1    168
I-2    174
F-1    364
F-2    464
F-3    564

Table 2 -- Composition of the Networks Studied

           D-1    D-2    T-1    I-1    Diol/Triol Ratio
           (g)    (g)    (g)    (g)    (mol OH/mol OH)

Coating 1  25.32          9.10   8.56  1/1
Coating 2  25.26         27.11  16.80  1/3
Coating 3         13.76   9.06   8.44  1/1
Coating 4          6.78  13.53   8.40  1/3

           -NHCO-           [M.sub.c]
           (mol/g Network)  (g * mol[.sup.-1])

Coating 1  0.0023           445
Coating 2  0.0029           377
Coating 3  0.0032           331
Coating 4  0.0034           312

Table 3 -- Contact Angles and Corresponding Surface Energies

           [[THETA].sub.water]   [[THETA].sub.diiodomethane]
           ([degrees])           ([degrees])

Coating 1   90.2 [+ or -] 1.7    67.2 [+ or -] 1.1
Coating 2   93.2 [+ or -] 2.0    68.9 [+ or -] 0.4
Coating 3  100.3 [+ or -] 1.4    69.8 [+ or -] 0.3
Coating 4  103.6 [+ or -] 0.5    71.2 [+ or -] 2.8

           [[sigma].sup.polar]  [[sigma].sup.disperse]
           (mN * [m.sup.-1])      (mN * [m.sup.-1])

Coating 1  3.4 [+ or -] 0.4     24.5 [+ or -] 0.6
Coating 2  2.7 [+ or -] 0.5     23.5 [+ or -] 0.2
Coating 3  1.1 [+ or -] 0.2     23.0 [+ or -] 0.2
Coating 4  0.7 [+ or -] 0.1     22.2 [+ or -] 1.6

               [[sigma].sup.total]
               (mN * [m.sup.-1])

Coating 1      27.9 [+ or -] 1.0
Coating 2      26.2 [+ or -] 0.8
Coating 3      24.1 [+ or -] 0.4
Coating 4      22.9 [+ or -] 1.4

Table 4 -- Composition of the Networks Studied

            D-1    D-2    T-1    T-2   I-1  I-2    F-1   -NHCO-
            (g)    (g)    (g)    (g)   (g)  (g)    (g)   (mol/g network)

Coating 11  16.67          9.03        8.4         4.86   0.0026
Coating 12   6.25         13.5         8.4         5      0.0030
Coating 13          9.16   9.03        8.4         4.86   0.0032
Coating 14          3.45  13.5         8.4         5.02   0.0033
Coating 21  16.67                2.24        8.72  4.84   0.0030
Coating 22   6.33                3.36        8.7   5.01   0.0042
Coating 23         15.95         3.57       13.98  7.78   0.0038
Coating 24          5.03         5.37       13.94  8.04   0.0049

Table 5 -- Contact Angles and Corresponding Surface Energies

            [[THETA].sub.water]   [[THETA].sub.diiodomethane]
            ([degrees])           ([degrees])

Coating 11  115.8 [+ or -] 1.5    98.2 [+ or -] 4.4
Coating 12  114.3 [+ or -] 0.3    97.4 [+ or -] 0.3
Coating 13  113.3 [+ or -] 0.1    97.7 [+ or -] 0.1
Coating 14  112.4 [+ or -] 0.4    97.2 [+ or -] 0.3
Coating 21  108.7 [+ or -] 0.2    87.2 [+ or -] 0.6
Coating 22  107.4 [+ or -] 0.2    91.7 [+ or -] 0.3
Coating 23  108.7 [+ or -] 0.1    88.9 [+ or -] 0.4
Coating 24  106.9 [+ or -] 0.1    92.9 [+ or -] 0.3

            [[sigma].sup.polar]  [[sigma].sup.disperse]
            (mN * [m.sup.-1])    (mN * [m.sup.-1])

Coating 11  0.8 [+ or -] 0.1      9.4 [+ or -] 1.7
Coating 12  0.9 [+ or -] 0.0      9.6 [+ or -] 0.1
Coating 13  1.1 [+ or -] 0.1      9.5 [+ or -] 0.1
Coating 14  1.3 [+ or -] 0.3      9.7 [+ or -] 0.1
Coating 21  1.1 [+ or -] 0.2     13.9 [+ or -] 0.3
Coating 22  1.7 [+ or -] 0.0     11.9 [+ or -] 0.1
Coating 23  1.2 [+ or -] 0.0     13.2 [+ or -] 0.2
Coating 24  1.9 [+ or -] 0.0     11.4 [+ or -] 0.1

            [[sigma].sup.total]
            (mN * [m.sup.-1])

Coating 11  10.2 [+ or -] 1.7
Coating 12  10.6 [+ or -] 0.1
Coating 13  10.6 [+ or -] 0.1
Coating 14  10.9 [+ or -] 0.2
Coating 21  14.9 [+ or -] 0.3
Coating 22  13.7 [+ or -] 0.1
Coating 23  14.4 [+ or -] 0.2
Coating 24  13.4 [+ or -] 0.1

Table 6 -- Composition of the Networks Studied

            D-2    T-2   I-2    F-1   F-2    -NHCO-
            (g)    (g)   (g)    (g)   (g)    (mol/g network)

Coating 54  13.94  5.37  13.94               0.0047
Coating 23  15.95  3.57  13.98  7.78         0.0038
Coating 24   5.03  5.37  13.94  8.04         0.0049
Coating 33  14.67  3.9   14.14         9.9   0.0037
Coating 34   5.51  5.35  13.94        10.82  0.0044

Table 7 -- Properties of the Fluorinated Coatings

            [[THETA].sub.water]  [[THETA].sub.diiodomethane]
            ([degrees])          ([degrees])

Coating 54   86.1 [+ or -] 1.2   47.7 [+ or -] 0.3
Coating 23  108.6 [+ or -] 0.1   88.9 [+ or -] 0.4
Coating 24  106.9 [+ or -] 0.1   92.9 [+ or -] 0.3
Coating 33  115.8 [+ or -] 0.2   99.5 [+ or -] 0.5
Coating 34  112.0 [+ or -] 0.3   97.4 [+ or -] 0.2

            [[sigma].sup.polar]  [[sigma].sup.disperse]
            (mN * [m.sup.-1])    (mN * [m.sup.-1])

Coating 54  2.4 [+ or -] 0.3     35.6 [+ or -] 0.2
Coating 23  1.2 [+ or -] 0.0     13.2 [+ or -] 0.2
Coating 24  1.9 [+ or -] 0.0     11.4 [+ or -] 0.1
Coating 33  0.9 [+ or -] 0.0      8.9 [+ or -] 0.2
Coating 34  1.3 [+ or -] 0.0      9.7 [+ or -] 0.1

            [[sigma].sup.total]  [[sigma].sup.disperse]/
            (mN * [m.sup.-1])    [[sigma].sup.total] (%)

Coating 54  37.9 [+ or -] 0.5             95
Coating 23  14.4 [+ or -] 0.2             92
Coating 24  13.4 [+ or -] 0.1             85
Coating 33   9.7 [+ or -] 0.2             91
Coating 34  10.9 [+ or -] 0.1             88

                   HM             E
            (N * m[m.sup.-2])   (GPa)

Coating 54  186.3 [+ or -] 3.4  2.45 [+ or -] 0.05
Coating 23   84.3 [+ or -] 7.0  1.03 [+ or -] 0.07
Coating 24  168.1 [+ or -] 3.7  2.08 [+ or -] 0.05
Coating 33   96.6 [+ or -] 5.9  1.22 [+ or -] 0.09
Coating 34  130.5 [+ or -] 3.5  1.72 [+ or -] 0.05

Table 8 -- Surface Free Energy of an Immersed Coating as a Function of
Immersion Time

                Glassy                  Coating 23
Immersion Time  [[sigma].sup.disperse]  [[sigma].sup.polar]
(min)           (mN * [m.sup.-1])       (mN * [m.sup.-1])

 0              13.2 [+ or -] 0.2       1.2 [+ or -] 0.0
 5              16.7 [+ or -] 0.1       2.1 [+ or -] 0.2
10              18.5 [+ or -] 0.3       2.2 [+ or -] 0.1
15              18.2 [+ or -] 0.1       2.4 [+ or -] 0.1
30              17.9 [+ or -] 0.3       2.8 [+ or -] 0.1
60              18.8 [+ or -] 0.3       2.1 [+ or -] 0.2

                Elastomeric             Coating 13
Immersion Time  [[sigma].sup.disperse]  [[sigma].sup.polar]
(min)           (mN * [m.sup.-1])       (mN * [m.sup.-1])

 0               9.5 [+ or -] 0.1       1.1 [+ or -] 0.0
 5              21.2 [+ or -] 0.3       6.2 [+ or -] 0.6
10              23.6 [+ or -] 0.3       6.2 [+ or -] 0.9
15              25.7 [+ or -] 0.3       5.1 [+ or -] 1.2
30              27.2 [+ or -] 0.5       4.6 [+ or -] 1.1
60              30.2 [+ or -] 1.2       4.7 [+ or -] 0.9

ACKNOWLEDGMENT 

This project was supported by the IOP Milieutechnologie (IZW99122), Senter, The Netherlands.

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Marielle Wouters, ([dagger]) Joyce van Zanten, Frank Huijs, and Teun Vereijken -- TNO Industrial Technology*

* Department of Polymer Technology, P.O. Box 6235, 5600 HE Eindhoven, The Netherlands.

[dagger] Author to whom correspondence should be addressed. Email: [e-mail].