Patent Description:
In particular, the PPO film has a surface area equal to or greater than <NUM><NUM>/g. More particularly, the procedure comprises the absorption/desorption of host molecules (guests) by an amorphous PPO film with particular conditions of crystallization kinetics induced by the guest.

Crystalline nanoporous phases are characterized by the presence of molecular-size cavities, which can be used for hosting and possibly releasing host molecules with low molecular mass.

Crystalline nanoporous phases are well-known for two commercial polymers, syndiotactic polystyrene and poly(<NUM>,<NUM>-dimethyl-<NUM>,<NUM>-phenylene)oxide (commonly known as polyphenylene oxide or by means of the acronym PPO).

In the scientific literature article <NPL> it is described that the PPO comprises two crystalline nanoporous forms, respectively termed form α and form β, easily recognizable by applying the WAXD (wide-angle X-ray diffraction) and FTIR (Fourier transform infrared) techniques).

Such crystalline nanoporous phases are obtained starting from co-crystalline phases, i.e. from crystalline phases which contain host polymer chains and guest molecules with low molecular mass. The obtainment of crystalline nanoporous phases occurs following the removal of the host molecules from co-crystalline phases, with suitable techniques, such as for example shown in the patent <CIT> or in the scientific literature article <NPL>.

Such crystalline phases are characterized by the presence of molecular-size cavities, which can be used for hosting and possibly releasing guest molecules with low molecular mass.

It is also well-known that also the PPO amorphous phase is nanoporous, since it is also capable of absorbing great quantities of guest molecules even if, generally, in lower quantities than the crystalline nanoporous phases, as shown for example in the scientific literature article <NPL>.

Specimens of PPO with crystalline nanoporous phases, if produced in the form of powders and aerogel, can have surface areas even greater than <NUM><NUM>/g (evaluated by means of the BET method) and consequently have high kinetics of absorption of guest molecules, as shown in the scientific literature article <NPL>.

Nevertheless, the powders are easy to handle for many applications while the aerogels have a very low density, typically lower than <NUM>/cm<NUM>, and therefore they have low absorption of guest molecules per volume unit.

For many devices for molecular separation, nanofiltration as well as for molecular sensors it is often suitable to use films which can be easily handled and have density close to <NUM>/cm<NUM>.

Nevertheless, it is well-known that in the case of films, diffusiveness of the guest molecules is generally observed that is reduced by various orders of magnitudes, with respect to those of aerogels (as described for example in the work <NPL>). Nanoprous PPO films have been prepared in the work of <NPL>.

In the case of PPO film, the surface area is generally negligible, i.e. below the sensitivity of the BET method (generally <NUM><NUM>/g). It is also well-known that for syndiotactic polystyrene, i.e. the other polymer which has crystalline nanoporous forms, the surface areas of the films are always smaller than <NUM><NUM>/g.

The Applicant has surprisingly observed that by carrying out the operations of absorption and desorption of host molecules on amorphous PPO film in particular conditions, it was possible to obtain PPO films with high surface area.

In particular, the Applicant has observed that the surface area of the resulting PPO film was considerably increased when the step of absorption of the host molecule with formation of co-crystalline phases is conducted with a crystallization rate equal to or greater than <NUM> percentage points per minute up to reaching a percentage of crystallinity higher than <NUM>%, preferably higher than <NUM>%, by absorption of a quantity of host molecules equal to or higher than <NUM>% w/w, preferably higher than <NUM>% w/w. At the same time, the Applicant has observed that the surface area of the resulting PPO film was considerably increased when the total removal of the host molecules absorbed during the step of absorption was carried out before the verification of a partial desorption, in particular before the content of said host molecules had fallen below <NUM>% w/w.

Therefore, a first aspect of the present invention is represented by a procedure for preparing a polyphenylene oxide (PPO) film with crystalline nanoporous phases, comprising the following steps:.

In a first embodiment of the first aspect of the present invention said host molecules have a molecular volume greater than <NUM><NUM>.

In a second embodiment of the first aspect of the present invention said host molecules are molecules of organic compounds, preferably selected from the group that comprises or consists of carvone, limonene, dibenzyl ether, eugenol, carvacrol, methyl benzoate and mixtures thereof.

In a third embodiment of the first aspect of the present invention, said step of formation of co-crystalline phases takes place at a temperature equal to or greater than <NUM>.

In a fourth embodiment of the first aspect of the present invention, said preparation of an amorphous PPO film is carried out by melt casting and subsequent cooling or by solution casting and subsequent evaporation of the solvent.

In a fifth embodiment of the first aspect of the present invention, said amorphous PPO film is a self-supporting film or a coating of a substrate.

In a sixth embodiment of the first aspect of the present invention, said total removal of said host molecules occurs by absorption followed by desorption of host molecules of a volatile liquid compound.

In a seventh embodiment of the first aspect of the present invention, said total removal of said host molecules takes place by supercritical CO<NUM> extraction.

In an eighth embodiment of the first aspect of the present invention, said total removal of said host molecules occurs before the content of said host molecules has dropped below <NUM>% w/w, preferably below <NUM>% w/w, more preferably below <NUM>% w/w, and still more preferably below <NUM>% w/w.

In addition, a second aspect of the present invention is represented by a polyphenylene oxide (PPO) film with surface area equal to or greater than <NUM><NUM>/g.

In a first embodiment of the second aspect of the present invention, said crystalline nanoporous phases have a percentage of crystallinity higher than <NUM>%, preferably higher than <NUM>%, more preferably higher than <NUM>%.

In a second embodiment of the second aspect of the present invention, said polyphenylene oxide film is a self-supporting film or a coating of a substrate.

In a third embodiment of the second aspect of the present invention, said substrate is made with a material selected from the group that comprises polymers, ceramics, glass, graphite, quartz, silicon and mixtures thereof.

In a fourth embodiment of the second aspect of the present invention, said crystalline nanoporous phases comprised in the PPO film are in alpha form.

In a fifth embodiment of the second aspect of the present invention, said polyphenylene oxide (PPO) film has a surface area equal to or greater than <NUM><NUM>/g.

In a sixth embodiment of the second aspect of the present invention, said polyphenylene oxide (PPO) film has a thickness equal to or greater than <NUM>, thickness equal to or greater than <NUM>, preferably equal to or greater than <NUM>.

The present invention relates to a procedure for preparing a polyphenylene oxide (PPO) film with crystalline nanoporous phases, comprising the following steps:.

The first step of the procedure of the present invention provides for the preparation of an amorphous PPO film.

The preparation of an amorphous PPO film is carried out by means of melt casting and subsequent cooling or by solution casting and subsequent evaporation of the solvent.

The casting can be attained as coating deposited on a suitable substrate, such as for example a substrate made with a material selected from the group that comprises ceramics, glass, graphite, quartz, silicon, polymers, such as for example ethylene polymers and copolymers, propylene polymers and copolymers, lactic acid polymers, polyamides, and mixtures thereof.

Any melt casting procedure leads to the formation of an amorphous PPO film, while the obtainment of amorphous PPO films by solution casting requires a suitable selection of the solvent, of the concentration and of the procedure temperature. The solvent is preferably selected from the group that comprises or consists of organic solvents, such as for example chloroform, dichloromethane, tetrachloromethane, dichloroethane, trichloroethane, trichloroethylene, benzene, o-dichlorobenzene, trichlorobenzene, toluene and methyl benzoate. The concentration of the PPO in the solvent are preferably selected in the interval from <NUM>% to <NUM>%, preferably from <NUM>% to <NUM>% by weight with respect to the weight of the resulting solution. The temperature of evaporation of the solvent is preferably higher than the room temperature, preferably higher than <NUM>.

The second step of the procedure of the present invention provides for the formation of co-crystalline phases by absorption of host molecules, preferably molecules of an organic compound.

The host molecules preferably have a molecular volume greater than <NUM><NUM>, more preferably greater than <NUM><NUM>.

The molecular volume of the host molecule can be calculated by means of the following equation: <MAT> where M and δ are respectively the molecular mass and the density of the host molecule, and NA is the Avogadro's number (<NUM>. 022x10<NUM>).

The absorption of the host molecules can be carried out via immersion in a liquid or via vapor exposure, preferably via immersion in a liquid. The liquid can be constituted by the pure organic compound or by a solution thereof in inert solvent, i.e. unable to be absorbed.

The absorption of the host molecules can be carried out up to a host molecule content equal to or higher than <NUM>% w/w, preferably equal to or higher than <NUM>% w/w, more preferably equal to or higher than <NUM>% w/w, and still more preferably equal to or higher than <NUM>% w/w.

Advantageously, the absorption of the host molecules can be carried out up to a host molecule content comprised between <NUM>% and <NUM>% w/w, in particular between <NUM>% and <NUM>% w/w, ends included.

The formation of co-crystalline phases preferably occurs with a crystallization rate equal to or greater than <NUM> percentage point per minute, more preferably equal to or greater than <NUM> percentage points per minute, and still more preferably equal to or greater than <NUM> percentage points per minute.

The crystallization rate can be controlled by varying the temperature and/or by using suitable organic compounds or mixtures thereof, and/or by varying the physical state of the guest (liquid, vapor, gas).

Advantageously, the step of absorption takes place at a temperature equal to or greater than <NUM>, preferably equal to or greater than <NUM>, more preferably equal to or greater than <NUM>.

Preferably, the organic compounds used are carvone, limonene, dibenzyl ether, eugenol, carvacrol, methyl benzoate, mixtures thereof and their solutions in inert solvents.

The third step of the procedure of the present invention provides for the transformation of the co-crystalline phases in crystalline nanoporous phases, by total removal of the host molecules.

With the expression "total removal of the host molecules" it is intended the reduction of the concentration of the host molecules to a percentage at least equal to or lower than <NUM>% w/w, preferably equal to or lower than <NUM>% w/w.

The total removal of the host molecules can be carried out.

The absorption/desorption procedure which uses a volatile liquid compound is preferably conducted at temperatures comprised between <NUM> and <NUM>, more preferably between <NUM> and <NUM>. Preferably, the volatile liquid useful in the present invention is selected from the group that comprises or consists of acetonitrile, acetone, methyl ethyl ketone and methanol.

Advantageously, the extraction procedure which uses supercritical CO<NUM> is conducted under pressure, preferably at values comprised between <NUM> and <NUM> bar, more preferably between <NUM> and <NUM> bar, at a temperature equal to or higher than the room temperature, preferably at values comprised between <NUM> and <NUM>, more preferably between <NUM>° and <NUM>, in a time period comprised between <NUM> and <NUM> minutes, preferably between <NUM> and <NUM> minutes.

The Applicant has observed that the removal of the host molecules also occurs spontaneously, i.e. via separation and detachment of the host molecules from the co-crystalline structure caused by the simple exposure to environmental conditions. The Applicant has also observed that the resulting surface area depends on the quantity of residual host molecules present in the co-crystalline phases before the total removal of the host molecules.

In particular, the Applicant has observed that the total removal of the host molecules must be carried out before the content of the same host molecules has dropped below <NUM>% w/w.

Preferably, the total removal of the host molecules must be carried out before the content of the same host molecules has dropped below <NUM>% w/w, preferably below <NUM>% w/w, more preferably below <NUM>% w/w, and still more preferably below <NUM>% w/w. Advantageously, the total removal of the host molecules must be carried out before the content of the same host molecules has dropped below a value comprised between <NUM>% and <NUM>% w/w.

The total removal of the host molecules can be carried out in one or more steps. The total removal can be conducted in multiple steps, as long as the last step starts from a host molecule content higher than <NUM>% w/w, preferably higher than <NUM>% w/w, more preferably higher than <NUM>% w/w. Preferably, the total removal of the host molecules is carried out in a single step. The Applicant has in fact observed that the total removal of the host molecules in a single step allows obtaining, the other conditions being the same, a higher surface area.

The polyphenylene oxide (PPO) film with surface area equal to or greater than <NUM><NUM>/g of the present invention can be in the form of self-supporting film or coating of a substrate.

The crystalline nanoporous phases comprised in the PPO film can be the alpha form (α) and/or the beta form (β) identified and described in the scientific literature article <NPL>.

Preferably, the crystalline nanoporous phases comprised in the PPO film are in alpha form.

The polyphenylene oxide (PPO) film of the present invention can have a surface area equal to or greater than <NUM><NUM>/g, preferably equal to or greater than <NUM><NUM>/g, more preferably equal to or greater than <NUM><NUM>/g, and still more preferably equal to or greater than <NUM><NUM>/g.

Advantageously, the polyphenylene oxide (PPO) film of the present invention has a surface area comprised between <NUM><NUM>/g and <NUM><NUM>/g, in particular between <NUM><NUM>/g and <NUM><NUM>/g.

The percentage of crystallinity of the crystalline nanoporous phases of the PPO film of the present invention is preferably equal to or higher than <NUM>%, more preferably higher than <NUM>%, and still more preferably higher than <NUM>%.

The percentage of crystallinity per PPO film is measured by means of differential scanning calorimeter measurements (DSC), by evaluating the enthalpy of fusion of the specimen and assuming that the enthalpy of fusion of a completely crystalline specimen is equal to <NUM> J/g.

The thickness of the polyphenylene oxide (PPO) film with surface area equal to or greater than <NUM><NUM>/g of the present invention is not particularly limited. Preferably, the polyphenylene oxide (PPO) film of the present invention has a thickness equal to or greater than <NUM>, preferably equal to or greater than <NUM>, more preferably equal to or greater than <NUM>, and still more preferably equal to or greater than <NUM>. Advantageously, the polyphenylene oxide (PPO) film of the present invention has a thickness comprised between <NUM> and <NUM>, in particular from <NUM> to <NUM>, ends included.

The polyphenylene oxide (PPO) film with surface area equal to or greater than <NUM><NUM>/g of the present invention is adapted to be used for various applications, for example in membrane for molecular separation, preferably with gas, molecular sensors, preferably of optical nature, and in filters, and more generally in systems, multiple for the removal of organic pollutants from the air and from the water.

The present invention will now be illustrated with reference to materials and methods described as a non-limiting example in the following experimental part.

A first PPO film (Film a) with thickness of <NUM> and alpha crystalline nanoporous phase was obtained by means of a three-step procedure:.

A second PPO film (Film b) with thickness of <NUM> with alpha crystalline nanoporous phase was obtained with the same procedure, except for step <NUM>, substituted with the following step <NUM>'. Step <NUM>'. Total extraction of the carvone by absorption/desorption of acetonitrile at room temperature.

The X-ray diffraction figures of such films have shown the presence of the diffraction peaks at 2θ = <NUM>°, <NUM>°, <NUM>°, <NUM>°, <NUM>°, indicating the presence of the alpha crystalline nanoporous form. Differential calorimeter scans have shown an enthalpy of fusion for the two films close to <NUM> J/g, corresponding to a crystallinity of about <NUM>%. The measurement of the crystallization rate detected a rate higher than <NUM> percentage points of crystallization per minute.

The isotherms of nitrogen absorption at <NUM>°K of such PPO films, of the amorphous PPO film (Film d), and of a PPO aerogel (Aerogel c) with density equal to about <NUM>/cm<NUM> and porosity equal to about <NUM>% are illustrated in <FIG>. The BET surface area values obtained from the data reported in <FIG> are summarized in the following Table <NUM>.

The results of table <NUM> demonstrate the surprising result obtained with the procedure of the present invention, i.e. the obtainment of a film with surface area equal to or greater (for films a and b) than that of an aerogel (Aerogel c) starting from a surface area smaller than <NUM><NUM>/g of the amorphous PPO (Film d).

For the same specimens, the kinetics of absorption of perchloroethylene (PCE) at <NUM> for W/Wo = <NUM> and the sum of PCE absorbed after <NUM> hours with various activities (W/Wo ≤ <NUM>) are respectively shown in <FIG> and <FIG>.

The quantity of PCE absorbed by the crystalline nanoporous films (Films a and b) has proven to be much higher than that of the amorphous PPO film having the same thickness (Film d).

Surprisingly, the absorption of PCE in the crystalline nanoporous PPO film obtained with the procedure <NUM>-<NUM> (Film a), with a greater surface area, was higher and faster than the absorption of PCE in the PPO aerogel (Aerogel c).

<FIG> reports the progression of the absorption of PCE at room temperature by aqueous solutions with PCE concentration equal to 50ppm for specimens of the aforesaid Films a and d and of the Aerogel c.

Also in this case, the crystalline nanoporous PPO film with high surface area (Film a) has an absorption that is much higher and faster than that observed for the amorphous PPO film (Film d), but also with respect to the PPO aerogel (Aerogel c).

A PPO film with thickness of <NUM> with alpha crystalline nanoporous phase was obtained with the same procedure described in steps <NUM> and <NUM> of example <NUM>.

The step of extraction of the carvone is conducted before the procedure <NUM>', but after a partial desorption of the carvone at room temperature, i.e. after the carvone content has spontaneously reduced from <NUM>% w/w to <NUM>% w/w.

The analysis of the X-ray diffraction conducted on the resulting PPO film has shown the presence of the diffraction peaks typical of the alpha crystalline nanoporous form, and the differential calorimeter scans detected a crystallinity of about <NUM>%, with a rate higher than <NUM> percentage points of crystallization per minute, but the measurement of the BET surface area obtained from the values of nitrogen absorption at <NUM>°K detected values lower than <NUM><NUM>/g, much lower than the values obtained in the example <NUM> with the film (b), and comparable to the values obtained with the amorphous PPO (Film d).

A PPO film with thickness of <NUM> with alpha crystalline nanoporous phase was obtained with the same procedure described in the steps <NUM> and <NUM>' of example <NUM>, while step <NUM> was conducted with liquid carvacrol at room temperature per <NUM> minutes, reaching a carvacrol content equal to about <NUM>% w/w.

The percentage of crystallinity reached did not exceed <NUM>%, with a crystallization rate equal to about <NUM> percentage points of crystallization per minute, and the BET surface area was smaller than <NUM><NUM>/g.

A first PPO film (Film <NUM>) with thickness of <NUM> and alpha crystalline nanoporous phase was obtained by means of a three-step procedure:.

A second PPO film (Film <NUM>) with thickness of <NUM> with alpha crystalline nanoporous phase was obtained with the same procedure, except for step <NUM>, substituted with the following step <NUM>'. Step <NUM>'. Total extraction of the limonene by absorption/desorption of acetonitrile at room temperature.

As for example <NUM>, the X-ray diffraction figures of such films have shown the presence of the diffraction peaks typical of the alpha crystalline nanoporous form. The differential calorimeter scans have demonstrated a crystallinity of about <NUM>%. The measurement of the crystallization rate detected a rate higher than <NUM> percentage points of crystallization per minute. The BET surface area values of Films <NUM> and <NUM>, obtained from the data of nitrogen absorption at <NUM>°K as described in example <NUM>, are summarized in the following Table <NUM>.

A comparison film attained with the same procedure of the film <NUM>, but by conducting step <NUM> at room temperature, allowed reaching a content of limonene of about <NUM>% w/w and a percentage of crystallinity of <NUM>% with a crystallization rate lower than <NUM> percentage points of crystallization per minute. The BET surface area value obtained for this comparison film was smaller than <NUM><NUM>/g.

On the contrary, a film of the invention, attained by using carvacrol with the same procedure of the film <NUM>, has demonstrated results that are substantially equal to those of the film <NUM>.

A PPO film with thickness of <NUM> and alpha crystalline nanoporous phase was obtained by means of a three-step procedure:.

As for example <NUM>, the X-ray diffraction figure of such film has shown the presence of the typical diffraction peaks of the alpha crystalline nanoporous form. The differential calorimeter scanning has demonstrated a crystallinity of about <NUM>%. The measurement of the crystallization rate has detected a rate higher than <NUM> percentage points of crystallization per minute.

The BET surface area value of the resulting film, obtained from the data of nitrogen absorption at <NUM>°K as described in example <NUM>, was equal to <NUM><NUM>/g.

A comparison film attained with the same procedure, but by conducting step <NUM> at room temperature, allowed reaching a carvone content of about <NUM>% w/w and a percentage of crystallinity of <NUM>% with a crystallization rate lower than <NUM> percentage points of crystallization per minute. The BET surface area value made for this comparison film was smaller than <NUM><NUM>/g.

The absorption capacity of the film (a) obtained in example <NUM> was evaluated by carrying out five cycles of PCE absorption/desorption conducted at a temperature of <NUM> and values of W/W<NUM> activity equal to <NUM>.

The results illustrated in <FIG> demonstrated that the Film (a) maintains its absorption capacity even after repeated cycles.

A PPO film with thickness of <NUM> with alpha crystalline nanoporous phase was obtained with the same procedure described in the steps <NUM> and <NUM>' of example <NUM>, while step <NUM> of co-crystallization was carried out by absorption of carvone from vapor phase <NUM> for <NUM> hour, reaching a carvone content equal to about <NUM>% w/w.

As for example <NUM>, the X-ray diffraction figure of such film has shown the presence of the diffraction peaks typical of the alpha crystalline nanoporous form. The differential scanning calorimeter has demonstrated a crystallinity of about <NUM>%. The measurement of the crystallization rate detected a rate higher than <NUM> percentage points of crystallization per minute.

The BET surface area value of the resulting film, obtained from the data of nitrogen absorption at <NUM>°K as described in example <NUM>, was equal to about <NUM><NUM>/g.

A PPO film with thickness of <NUM> and alpha crystalline nanoporous phase was obtained by means of a three-step procedure similar to that of example <NUM>, with the following conditions:.

A film of a mixture of PPO and atactic polystyrene (PS) in a weight ratio equal to <NUM>/<NUM> with thickness of <NUM> and alpha crystalline nanoporous phase was obtained by means of a three-step procedure similar to that of example <NUM>, with the following conditions:.

As for example <NUM>, the X-ray diffraction figure of such film has shown the presence of the typical diffraction peaks of the alpha crystalline nanoporous form. The differential scanning calorimeter has demonstrated a crystallinity of about <NUM>%. The measurement of the crystallization rate detected a rate higher than <NUM> percentage point of crystallization per minute.

Claim 1:
A procedure for preparing a polyphenylene oxide (PPO) film with crystalline nanoporous phases, including the following steps:
• preparation of an amorphous PPO film,
• formation of co-crystalline phases with a percentage of crystallinity higher than <NUM>% by absorption of host molecules,
• formation of crystalline nanoporous phases by total removal of said host molecules,
characterized in that
said absorption of host molecules is conducted up to a host molecule content equal to or greater than <NUM>% w/w,
said formation of co-crystalline phases occurs with a crystallization rate equal to or greater than <NUM> percentage points per minute, and
said total removal of said host molecules occurs before the content of said host molecules has dropped below <NUM>% w/w, the percentage of crystallinity being measured as disclosed in the description.