PROTAVIC SG (SOL-GEL) : AN EASY ACCESS TO ADVANCED FUNCTIONAL MATERIALS

A - INTRODUCTION: PROTAVIC AND SOL-GELS

A-1 AN INTEGRATED WHOLE

PROTAVIC is the Integrated Chemical Company for sol-gels.

PROTAVIC offers the following range of products for sol-gel techniques:

- PROTAVIC PSG: Organometallic Precursors of metallic oxides.
- PROTAVIC HSG: Hybrid precursors for inorganic/organic hybrid materials.
- PROTAVIC OSG: Metallic Oxides, as oligomers solution, colloidal suspension or powder, obtained by the sol-gel process.
- PROTAVIC SGF: Ready to use Formulations and solutions, which are intended to bring a precise Functionality and which are entirely suitable for industrial processes.

In addition PROTAVIC, as part of the PROTEX INTERNATIONAL group, offers a fully integrated chemical service in the field of sol-gel:

- Development : A research and development team specifically devoted to sol-gels and precursors, which can - if necessary - draw on a external network of collaborative links and contacts with a long experience of chemistry and sol-gel processes.

- Production on both pilot scheme and industrial scale : PROTAVIC, as a subsidiary of the PROTEX INTERNATIONAL group, has at it disposal a whole range of plant and equipment (size, nature...), synthesizing processes (organic, inorganic...), analytical and application resources and expertise which enable it to offer optimum solutions for perfecting products which are the result of either internal developments or ones specific to our customers, right through from initial development to the pilot scheme stage and then on to the industrial scale.

A-2 SOL-GEL PROCESS

The sol-gel process is a chemical way for the synthesis of materials, of oxide and/or hybrid type, using as a base a solution containing reactive precursors - mainly alkoxyde (OR, R = Me, Et, Pr, Bu...) metallic (M = Si, Ti, Zr, Ta, Pb, Sn, Al, B, Sb, In, Ba, Sr, Bi, V, Ru, Hf, Mg...). Such precursors may have the following structure:

Monometallic : M(OR)_n     M(OR)_n-x(OR')_x     M(OR)_n-xR'_x
Multimetallic : MM'(OR)_n-x(OR'')_x ...

Material synthesis

Synthesis, which is in fact a polymerisation process, is then achieved in two stages :

- an initiation stage, in general, a hydrolysis (the water acts as a reagent, to form a reactive function M-OH).
     -M-OR + H₂O-M-OH + ROH

- and a propagation or condensation stage (formation of a solid network via oxygen bridges).
     -M-OH + M-OH-M-O-M- + H₂O
     -M-OH + -M-OR-M-O-M- + ROH

Depending on the nature of the chemistry of the formulation, the material is formed following two possible methods:
- The polymeric method consists of producing a solution of precursor material, which - when applied on the substrate - is converted into dense, strong oxide.
- The colloidal method starts out with the preparation of a suspension of fine particles (between 1 nm and 1 µm) dispersed in a suitable liquid medium. In this case the conversion into oxide is achieved chemically (in solution) before being deposited on the substrate. The material is then relatively porous.

Then, according to the method of drying, the sol-gel transition may give powders, solid materials, aerogels, fibres, thin layers and films.
Finally, in certain cases, the application of heat is needed to obtain a material which as the desired properties (the temperature required will vary accordingly). For example, for curing a ceramic, the temperature required is several hundred degrees lower than those used for conventional fritting processes.

A versatile process

The chemical and physical nature of the sol-gel formulation makes it a very versatile approach for the preparation of coating.
This flexibility is particularly true in term of:

COMPOSITION & STRUCTURE OF THE FILM
- From pure inorganic to organic/inorganic hybrid materials.
- Thickness from nanometre to millimetre (depending on composition).
- Internal structure: Powdery; Porous (nano, meso, ultra); Dense.

DEPOSITION METHOD versus SHAPE & SIZE OF THE SUBSTRATE
- Solution for dip, spin, spray or enduction coating.
- For substrate from nanometre to meter size.

DEPOSITION & CURING CONDITIONS versus COMPOSITION OF THE SUBSTRATE
- Atmospheric pressure
- Temperature/UV curing depending on material, substrate and targeted performance.
- Ceramic, glass, Crystal / Metal / Polymer, Rubber, Plastic / Composite.

B PROTAVIC PRODUCTS

B-1 PROTAVIC PSG: Sol-Gel Precursors

Sol-gel process is a technique of choice for making ceramic, glass and hybrid material from solutions containing reactive organometallic precursors.
They are mainly alkoxyde, beta-diketonate, carboxylate and other ligands may be used.
These precursors react in presence of water or humidity following the hydrolysis-condensation sequence to form the final material, usually a metallic oxide.
Typical examples of metal (M) or substituant (OR) available are:

- M = Al, Ba, Bi, Ce, Cu, Er, Fr, Ga, Ge, Hf, In, La, Mg, Mn, Nb, Nd, Ni, Pb, Pr, Sb, Si, Sn, Sr, Ta, Ti, V, W, Y, Yb, Zn, Zr...

- OR = Alkoxyde (OMe, OEt, OPr, OBu...), Carboxylate ( ethylhexanoate...), beta-diketonate (acac...)

Some metallic alkoxyde are particularly sensitive to humidity. In that case we may propose stabilised molecular precursors that will facilitate the manipulation of such products in laboratory or industrial environment.

The range of PROTAVIC PSG products is offering already a large choice of metal type, currently referenced under the name PROTAVIC PSG Ee, where Ee refers to the name of the metal.

B-2 PROTAVIC HSG: Hybrid Organic/Inorganic Precursors

The sol-gel process gives access to a new class of materials, known as hybrids, since they combine - on a submicronic scale - inorganic (cluster, aggregate, macromolecules) and organic constituents (molecules, oligomer, polymer).

They are two major classes of hybrid materials : class I ; class II.

Class I hybrid materials :
In this case the two constituents have weak interactions between them (van der Waals, electrostatic, hydrogen bond). Such materials can be prepared, amongst other methods, by adding the appropriate organic molecule into the sol-gel formulation.

Class II hybrid materials :
In this case the organic and inorganic parts have covalent or ionocovalent bonds between them. Such materials can be prepared from heterofunctional precursors (R_xM(OR)_n-x), or by organic postfunctionalisation of preformed mineral objects (grafting onto the surface of a nanoparticle, graftable cluster...).

The nature, size and proportions of each constituent can be adjusted precisely and independently thus opening up a whole class of materials with new properties.

One can thus theoretically pass by a continuous gradual progression from 100% inorganic materials to 100% organic materials. This makes it possible, in many cases, to keep the best of each of the constituents such as : hardness or abrasion resistance for the inorganic one (eg : SiO₂) and ease of shaping or flexibility for the organic one.

Formulation chemistry and fine chemistry

Such a diversity is to be found in the chemical composition of the precursors and solutions used.

For class I materials, precise formulation work makes it possible to arrive at the right composition and the right morphology for each constituent. Formulation can be prepared from PROTAVIC PSG or OSG products

For class II materials, it requires the synthesis and use of PROTAVIC HSG hybrid precursors, which have around the metallic nucleus, alkoxyde substituants (precursor of the oxide) and organic substituants (alkyl, aromatic, epoxy or acrylic type polymerisable function, optically active, surface-active, etc.).

The range of PROTAVIC HSG products is offering already a large of organic function, currently referenced under the name PROTAVIC HSG hhh, where hhh refers to the type of organic molecule linked to the Si atom.

B-3 PROTAVIC OSG: Oligomeric or Colloidal Metal Oxide

Some metallic alkoxyde, if they are not properly stabilized, may be very sensitive to humidity. In that case the manipulation of such products if possible in laboratory environment, may be difficult in some industrial environment.
PROTAVIC OSG products offer a solution to this problem.

Starting from pure molecular precursor (PROTAVIC PSG), we have performed the hydrolysis / condensation in a controllable way to get a stable and reproducible solution.
These solutions is composed of solvent (alcoholic, water) and metallic oxide under two possible forms:

- Oligomer / Polymer, having a size below 10 nm,
- Nanoparticle, having a size of few tens of nanometre, in colloidal suspension.

PROTAVIC OSG products can be used directly to prepare thin layer of the corresponding metallic oxide.
PROTAVIC OSG products can be also formulated with PROTAVIC PSG products or PROTAVIC HSG products, or any other chemicals compatible with the solvent used.

The range of PROTAVIC OSG products is offering already a large choice of metal type, currently referenced under the name PROTAVIC OSG Ee, where Ee refers to the name of the metal.

C FUNCTIONAL COATINGS: PROTAVIC SGF

PROTAVIC SGF have been developed to offer direct access to sol-gel techniques.

Each PROTAVIC SGF product offers a specific functionality and can be used to prepare thin layers. They have been specifically developed for an industrial use. They are ready to use, stable formulation.

The PROTAVIC SGF offers all the flexibility of the sol-gel chemistry to prepare functional thin film.

C-1 FUNCTIONAL PROPERTIES

The very wide diversity - in terms of the chemical composition of the materials, their form or their application process, which sol-gel processes allow - is mirrored in the multiplicity of applications, and in particular the multiplicity of functional properties which can be achieved.

Thus it is possible to confer to systems (material, multimaterial...), either by depositing thin layers or by using powders prepared by the sol-gel process, the following range of properties :

Reflection/Transmission Anti-reflective Reflective Filtering Decoration/Coloration Colouring Photochromic Thermochromic Active Electrochromic Luminescent Non linear optic Dielectric Insulating low k high k Conductive (transparent) Conductive (transparent) Antistatic (transparent) Semi-conductor Active Ferro-electric Piezo-electrical Pyro-electrical Impact resistance Micro hole filling Break-inhibiting Composite Surface resistance Anti-abrasion Anti-scratch Hardening Surface structure Controlled porosity Roughness, planarisation Lubricating Barrier Alkaline Humidity / Gas Anti-corrosion Surface tension Hydrophobic / Hydrophilic Oleophobic / Oleophilic (anti-dew, -soil, -adhesion) Primer Bonding preparation Adherent Functionalisation Photocatalytic Photodegradation Self cleaning Anti-microbial It is sometimes possible to combine within the same thin layer or system of thin layers, several functional properties : Non-reflective + Non-scratch ; Non-reflective + Antistatic ; Non-scratch + Barrier...

C-2 FIELDS OF APPLICATION

These functional properties find their applications in a large number of industrial sectors : Electronics (SiO₂ passivation, Insulation layer, planarisation, transparent electrode, dielectric for capacitors, ferroelectric for MEMS...), plastics (non-scratch plastic lens, antistatic foils, barrier to gas...), automotive industry (non-stain, photochromic...), glass (flask decoration, non-reflective windows, non breaking bottles...), cosmetics (nanopowders...), materials (anticorrosion, aluminium passivation...).

C-3 PROTAVIC® SG F ranges

PROTAVIC SG F offers a wide range of functionality:

PROTAVIC SG FA range Layers with low to high refractive index, for mono or multilayer anti-reflective system. PROTAVIC SG FB range Barrier layers (to alkaline, to corrosion...) PROTAVIC SG FC range Colored hybrid or inorganic layers (transparent, opaque, frosted...). PROTAVIC SG FD range Photocatalytic layers (photodegradation, self-cleaning, anti-microbial...) PROTAVIC¨ SG FE range Electroconductive and antistatic transparent coating, on polymer or glass substrate. PROTAVIC¨ SG FF range Ferroelectric, piezoelectric, pyroelectric, high k (PZT, PT...) Thin to thick layer. PROTAVIC SG FL range To improve adhesion of inorganic film on polymeric surface. PROTAVIC¨ SG FP range Photochromic hybrid thin layer with rapid transition (Patented). Activation in less than a second, deactivation in a few seconds. Blue, dark blue, grey colours. PROTAVIC¨ SG FS range Scratch resistant coating for PMMA, PC... Additive to reinforce scratch resistance of organic resin. PROTAVIC SG FW range Wetting layer by increase of the hydrophilicity of surface.