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1

Synthesis and characterization of heterocyclic-ORMOCERS composites

through Sol-gel process: A Review

Syed Salman Shafqat1, Sinin Hamdan

1, Andrew Ragai Henry Rigit

1,

Nicholas Kuan Hoo Tien1, Shanti Faridah Saleh

2, Amir Azam Khan

1*

1Department of Mechanical and Manufacturing Engineering, Faculty of Engineering,

Universiti Malaysia Sarawak (UNIMAS), 94300 Kota Samarahan, Sarawak, Malaysia 2Department of Chemical Engineering & Energy Sustainability

Universiti Malaysia Sarawak (UNIMAS), 94300 Kota Samarahan, Sarawak, Malaysia

* E-mail: akamir@feng.unimas.my

ABSTRACT

There is an enormous demand for Composites and Hybrid materials as many of the well-established

materials, such as metals, ceramics or plastics cannot fulfil all technological desires for the various new

applications. Sol–gel process has been extensively studied for several decades as a method to prepare

Composites and Hybrid materials. This paper presents a review on the basic concepts related to sol-gel

chemistry, major factors affecting the reaction kinetics and surface modification of silica network with

organofunctionalized groups for the preparation of homogeneous composites. The ORMOCERS based

composites have numerous applications, notably when grafted with heterocyclic amines. The insertion of

organometallic precursors in sol-gel process to get transition metal embedded ORMOCERS subsequently

grafted with heterocylic amines are proposed in this work. These composites and hybrid materials are

expected to be optically active within the visible range. These can be eventually used as optical brighteners

and dyes in the textile industry.

Key words: Sol-Gel, ORMOCERS, Hybrid Materials

1. Introduction Nanotechnology is continuously growing through all the fields related to science and technology such

as materials, electronic, aerospace, defence, medical, and dental etc. This technology comprises design,

synthesis, characterization, and application of material and devices on the nanometre scale [1]. Composites and

Hybrid material can show superior properties as compared with their pure counterparts. Properties of these

organic and inorganic composites are in between the two original phases or even exhibit new properties. Such

materials are lightweight with advanced mechanical properties [2]. Among the inorganic nanoscale building

blocks, SiO2 are viewed as being very important. Advancement in nanotechnology has led to the production of

nanosized silica, which is pure and produced mostly in amorphous powder form as compared to natural mineral

silica which are in crystalline forms and contain impurities and not suitable for advanced scientific and

industrial applications [3]. Recently numerous methods were explored and successfully used to produce

Organically modified Ceramics (ORMOCERS) as well as organic-inorganic hybrid materials. The sol-gel

process is widely used to produce pure silica particles, ORMOCERS as well as hybrid materials due to its

ability to control the particle size, size distribution and morphology through systematic monitoring of reaction

parameters.

2. Sol-Gel Process The sol-gel process is a wet-chemical technique widely used in the fields of materials

science and ceramic engineering at low temperature. The sol-gel technique, as a tool, to produce silica glass was

reported for the first time in 1846 by Ebelmen, when he obtained a solid matter by slow hydrolysis of ester of

silicic acid. Sol–gel process is chemically related to an organic polycondensation reaction in which

fabrication of materials (typically metal oxides) starting from a colloidal solution (sol) that acts as the precursor

for an integrated network (or gel) of either discrete particles or network polymers takes place [4].

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3. Sol-Gel Chemistry In laboratory conditions, the preparation of sol-gel system is performed by slow dropping of the

corresponding precursor to solvent system consisted on alcohols with addition of catalyst and water. The basic

steps in the sol-gel technologies are [5]:

3.1 Hydrolysis of precursor It is a reversible chemical reaction. The forward reaction in the first step is the hydrolysis of alkoxy

groups and the reverse reaction is called esterification reaction [6].

OR Si

OR

OR

OR + HO

H

H+/-OH

OR Si

OR

OR

OH + ROH (1)

3.2 Polymerization/ condensation The second step is the condensation reaction, which proceeds via two competitive mechanisms. In the

first mechanism, the forward reaction produces an alcohol accompanied by the reverse reaction called

alcoholysis reaction. The second mechanism involves the water producing forward step and corresponding

reverse reaction is called hydrolysis. The sequence of the reactions shown below does not accurately represent

the actual order of the sol-gel process. Although, hydrolysis reaction precedes the condensation reactions,

depending upon the conditions, it does not necessarily go to completion prior to the onset of condensation.

Alcohol condensation and Alcoholsis

RO Si

OR

OR

OR + RO Si

OR

OR

O Si

OR

OR

OR + ROHOH Si

OR

OR

OR (2)

Water condensation and Hydrolysis

RO Si

OR

OR

OH + RO Si

OR

OR

O Si

OR

OR

OR + HOHOH Si

OR

OR

OR (3)

The hydrolysis and polycondensation (water plus alcohol condensation) reactions initiate at numerous

sites within the alkoxide-water solution as the mixing occurs.

More than 40 elements are being used in the field of the sol-gel technologies. The introduction of

transition metal oxides such as Titania [7] or Zirconia [8] in hybrid materials like ethoxysilylterminated PDMS–

TEOS leads to an improvement in the mechanical properties of the hybrid elastomers. The ultimate strength and

elastic modulus increases in the presence of titania-based composites [8]. In 2001, F. Rubio et al., [9] reported

that the presence of TiO2 in ORMOCERS gives also a continuous decreasing in the pore connectivity. On the

other hand, density increases and porosity decreases with the TiO2 concentration. Y. Vahidshad et al., [10]

synthesized CuO–ZrO2 nanoparticles as catalyst for hydrogen production from methanol. Finer precursor

nanoparticles synthesized by sol-gel process give rise to larger specific areas in catalyst which result in a high

hydrogen production. In 2013, Hui Zhang et al., [11] reported that sol–gel dip-coating technique can be used to

fabricate SiO2–TiO2 composite film with self-cleaning and anti-reflectance properties from low-cost SiO2

colloid solution and Ti(OC4H9)4.

3.3 Ageing When a gel is maintained in its pure liquid, its structure and properties continue to change long after the

gel point. This process is called aging. Four processes can occur, singly or simultaneously, during aging,

including polycondensation, syneresis, coarsening, and phase transformation. Iler and Scherer [12] has made an

effort to describe aging phenomena theoretically, there is relatively little detailed knowledge of aging

mechanisms and kinetics and even less quantitative analysis of the effects of aging on gel structure and

properties. Polycondensation reactions continue to occur within the gel network as long as neighbouring silanols

are close enough to react. This increases the connectivity of the network and its fractal dimension. Syneresis is

the spontaneous shrinkage of the gel and resulting expulsion of liquid from the pores. Coarsening is the

irreversible decrease in surface area through dissolution and reprecipitation processes.

3.4 Drying Supercritical drying, freeze drying, spray drying, and thermal drying are some of the common

techniques used to produce particulate solid materials from the liquid phase. Collision and coalescence are the

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two main factors that govern the extent of agglomeration in a nanoparticles powder system. Also, the intense

ageing process that occurs during the drying of sol can lead to complex agglomeration behaviour arising from

polycondensation reactions and in some cases the polycondensation reactions between the silanol groups tend

increase in presence of water and catalyst. Thermochemical properties of silica polymer nanocomposite are

significantly reduced due to the presence of agglomerates. In aqueous system, the agglomeration behaviour was

found to be three time as compared to alcoholic medium. Rahman and co-workers [13] have reported that

alcohol dehydration was an effective technique to produce silica nanoparticles with improved dispersion and

reduced agglomeration.

4. Factors affecting the Sol Gel Process There is a wide range of factors which can affect the composition and properties of the product

obtained. Main factors are described as follows:

4.1 Precursors It is understood fact that the constitution of the obtained gel depends generally on the precursors, their

concentration, and the nature of the reactions between them. The precursors should be soluble in the liquid

medium to possess reactivity in the system. Most commonly used precursors are inorganic salts (e.g., nitrates,

chlorides) in aqueous solutions or metal organic compounds (e.g., alkoxides M(OR)Z) in non-aqueous solvents,

where M = Al, Sn, Ce, Ti, Zr, Hf, Si, etc., OR is an alkoxy group and Z is the valence or the oxidation state of

the metal or metalloid. Silicon alkoxides have a more controlled and lower reactivity than the other metal

alkoxides and hence the majority of the understanding of the sol-gel reaction is derived from materials created

from silicon-based alkoxides, such as tetramethoxysilane (TMOS; Si(OCH3)4) and tetraethoxysilane (TEOS;

Si(OC2H5)4). It has been noted that the alkyl radicals are so important for composition, structure and properties

of the product, so the kind of the metal ion in the corresponding alkoxides used. As well as, it is studied that the

length of the aliphatic chain has remarkable influence over the durability and protective ability of the coatings,

obtained from these compounds. Hasegawa and Sakka [14] have investigated the effect of alkyl group on

reactivity of precursors as:

Steric effects: branching and increasing of the chain length lowers the hydrolysis rate:

Si(OMe)4 > Si(OEt)4 > Si(OnPr )4 > Si(OiPr)4 > Si(OnBu)4 > Si(OHex)4

Inductive effects: electronic stabilization/destabilization of the transition state. Electron density at Si

decreases:

R-Si > RO-Si > HO-Si > Si-O-Si

Organometallic precursors are also frequently used, but the process is rather based on thermal

decomposition than sol-gel, but only two ways to include organometallic compounds inside amorphous silica

are known. One method used the precursor MLn-R2P(CH2)2Si(OEt)3, MLn = Fe(CO)5, RuCl2(η6-cymene),

Co2(CO)9, and other used the precursor cis- (Cl((CO)2P(R)(R')(CH2)xSi(OCH3)3 in the presence of TEOS.

Recently it is investigated that other organometallic precursors can also be used in sol gel process. Successful

results have been achieved to produce inorganic-organic hybrid nanocomposites, in 2012 [15] by inclusion of

the organometallic

MLn=HOC5H4N.Cp2TiCl][PF6] , HOC5H4N(CO)5, HOC5H4N.Mo(CO)5, [HOC6H4CH2CN.Cp2TiCl][PF6], HOC

6H4CH2CN.W(CO)5 and HOC6H4CH2CN.Mo(CO)5 into amorphous silica using the gelator precursor TEOS and

N3P3{NH[CH2]3Si[OEt]3}6. In the same year Carlos Dıaz, Marıa Luisa and Valenzuela [16] prepared metal–

organic nanocomposites by incorporating organometallic derivatives of the cyclotriphosphazene inside SiO2

through the sol–gel method.

4.2 Effect of Catalyst 4.2.1 Acid-Catalysed Reactions

Under acidic conditions (usually mineral acids), the hydrolysis reaction involves nucleophilic attack of

water on silicon atoms carrying a protonated alkoxide group. The transition state decays by displacement of an

alcohol and inversion of the configuration takes place. Condensation involves the attack of silicon atoms

carrying protonated alkoxide or silanol species by neutral Si-OH nucleophiles and displacing alcohol or water

molecules, respectively. Under acidic conditions, the rate of hydrolysis reaction is more efficient than the

condensation reaction. The most basic silanol species are those contained in monomers or weakly branched

oligomers. As a result, a bushy network of weakly branched polymer is obtained.

a) Hydrolysis

R

Si

R

R OR

R

Si O+

R

R

R

H

+ H+ +H2O

R

SiOH

R

R + ROH+ H+

Si

R R

CH3

O

R

O

H

H

R

+

(4)

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b) Polycondensation

R

Si

R

R OH ROH +H+

+R

Si

R

R O+

R

H R

Si

R

R O Si

R

R

R

+ (5)

R

Si

R

R OH H2O +H+

+R

Si

R

R O+

R

H R

Si

R

R O Si

R

R

R

+ (6)

Under acidic conditions +vely charged intermediate is formed, so the hydrolysis rate decreases with

each subsequent hydrolysis step as –OH group is replaced by –OR, and stability of intermediate is decreased.

Applying acid-catalyzed reactions an open network structure is formed in the first steps of the reaction leading

to condensation of small clusters[17]. The transparent nanocomposites with characteristic morphology sizes

below 100 nm are generally obtained in acid catalyzed reactions[18].

4.2.2 Base-Catalysed Reactions

In the presence of a base (ammonia), water is dissociated in a rapid first step to produce nucleophilic

hydroxyl ions, and hydrolysis is then initiated by the attack of this hydroxyl ion on the silicon atom. A SN2-type

mechanism has been proposed in which the hydroxyl ion displaces the alkoxy ion with inversion of the silicon

tetrahedron. The formation of siloxane (Si-O-Si) bonds occurs by an alcohol producing condensation reaction.

Iler proposed a mechanism that involves the attack of a nucleophilic deprotonated silanol (Si-O-) on a neutral

siloxane species. In the first step, silanoate ion is formed by deprotonation of a silanol. The ease of

deprotonation depends upon the other substituents attached to the silicon atom.

a) Hydrolysis

R

Si

R

R OR + OH- OH Si OR

R R

-

R

OH Si OR

R R

R

- + Si

R

R

ROH + RO-

(7)

b) Polycondensation

R

Si

R

R OH +-OH Si

R

R

O-

R + H2O (8)

R

Si

R

R OR + Si

R

RO-

R R

Si

R

R O Si

R

R

R

+ H2O (9)

Under basic conditions each subsequent hydrolysis step would occur more quickly as in this case –vely

charged transition state is formed and its stability decreases at each step. The base-catalyzed reaction leads to

highly cross linked sol particles[18]. It has been shown that basic catalysis usually yields opaque composites

with phase dimensions well above 100 nm and more generally in the micrometer range. These materials can

definitely not be considered as nanocomposites.

Shusen Peng et al., [19] reported that hybrid silica sol–gel coating was prepared using Ce(NO3)3 (Sol-

Ce) as catalyst. Ce(NO3)3 had a stronger influence on reactivity of alkoxysilane Sol-Ce coating had better

anticorrosion ability than Sol-Ac and Sol-Ac/Ce on carbon steel.

In some cases there is no need to add a catalyst as reaction is autocatalysed for example I.A. Rahman et

al., [20] prepared organofunctionalized silica in nanosize range with amine-terminated group without the

addition of ammonia as a catalyst. In this reaction amino group present in reactant itself acted as a catalyst.

4.3 Solvent Both protic and aprotic solvents are used in sol-gel process and may vary in their polarity. Protic

solvents form hydrogen bonding with both oxonium (H3O+) and hydroxyl ions (OH

-) catalysts, and reduce the

catalytic activity under acidic and basic conditions, respectively. Therefore, aprotic solvents that do not make

hydrogen bonding with hydroxyl ions make the hydroxyl ions more nucleophilic, whereas protic solvents make

oxonium ions more electrophilic. Likewise protic solvents capable of forming hydrogen bond to nucleophilic

deprotonated silanols, retard base catalysed condensation and promote acid-catalysed condensation. Aprotic

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solvents have the reverse effect. Artaki et al., [21] grouped the solvents and additives of their study into three

categories as polar protic, polar aprotic and non-polar aprotic. This study showed that the effective network of

intermolecular hydrogen bonding thus retards the condensation process and on the other hand, the absence of

hydrogen bonding results in a significant enhancement of the condensation rate. The efficient condensation,

therefore, leads to the formation of large, compact, polymeric particles.

4.4 Stoichiometry Since water is a reactant in aqueous sol-gel process, so H2O/Si ratio has a complex effect on the

reaction kinetics and on the final structure of the material. The overall trend which is evident from different

studies is that the higher the water to metal alkoxide ratio the faster is the rate of hydrolysis before significant

condensation occurs. Moreover the higher concentration of water causes more complete hydrolysis of the

monomers. Two effects on the condensation reactions are easily recognised that at low ratios the alcohol

producing condensation reactions are favoured while the water producing ones are favoured at high H2O/Si

ratios as well as large values of the ratio promote siloxane bond hydrolysis. As for the effects on gel structure,

Sakka et al., have reported that adding insufficient amount of water tends to promote linear structures. Because

water is produced as a by-product of condensation reaction, two moles of water for every one mole of tetra-

functional silicon alkoxide are theoretically sufficient for complete hydrolysis and condensation to yield

anhydrous silica as shown by the net reaction[14]:

nSi(OR)4 + 2H2O nSiO2 + 4nROH (10)

4.5 Temperature Temperature has a direct effect on gelation rate and the physical properties of the product in a sol-gel

process. Wesam A. A. Twej [22] has investigated the influence of temperature on the gelation times and the

physical properties of the produced from TEOS system. The observed trends showed that higher gelation

temperatures result in lower gelation times, higher bulk densities, and lower porosities of the xerogel materials.

5. Classification of products The sol gel route permits the development of entire new generations of advanced materials. S.

Kozhukharov [5] classified these materials into four classes. One of these classes is composed of entire

inorganic network. Usually, Tetramethoxysilane Si(OCH3)4 , Tetraethoxysilane Si(OC2H5)4 and Ti-isobutilate

Ti-butilate etc. are used as precursors to form such type of networks. Glasses and glass-ceramic materials with

large variety of applications are consisted on metal oxides as In2O3–SnO2, NaO2-B2O3-SiO2, SnO2-CdO, as well

as BaTiO3 and KTaO3 are described in the literature[23]. The second type includes the materials in which

inorganic network has surface modification of non-reactive organic group. These materials are now named as

“ORMONAN”-organically modified nanocomposite. Fabes et al., [24] as well as Malzbender [25] et al., studied

the mechanical properties of thin films prepared by sol–gel silicas modified by hydrophobic methyl group. Third

class is named as “ORMOCER” Organically Modified Ceramics. They form inorganic networks with reactive

organic groups which are available modification for crosslinking/polymerization reactions, or organic

monomers/polymers with silylated and groups for crosslinking/co-condensation via inorganic Si–O-Si bonds.

The uniting feature of those substances is the bonding between the organic network and the inorganic lattice,

which allows the creation of entirely new generation of advanced materials. These materials are mostly used as

protective coatings as described by Guglielmi. The materials of this type also form the basis of obtaining of

hybrid polymers.

The incorporation of functionalities into silica network can be achieved in three ways: by grafting, by

co-condensation and by the use of bissilylated organic precursors[26].

Typical examples of class four are the gels obtained by Organic monomers which react via chemical

crosslinking or polymerization reactions. This method could be modified depending upon the nature and number

of functional groups of the corresponding precursors. This number of functional groups predetermines directly

whether the polymeric structure will be linear or cross-linked (branched) [5].

6. Characterization: Different characterization techniques are being used to analyse the chemical structure, microstructure,

morphology, and thermal properties of ORMOCERS. The most widely employed methods to characterize these

material include small-angle X-ray scattering (SAXS), neutron scattering (SANS) and light scattering (SALS),

nuclear magnetic resonance NMR, Fourier transform infrared FTIR, Mass and fluorescence spectroscopy, BET

adsorption experiments, differential thermogravimetric analysis, and impedance spectroscopy . Characterization

of few representative organically modified ceramics is described as follows.

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A photoresponsive coumarin derivative was grafted on the pore outlet of Si-MCM-41[27]. Irradiation of

UV light longer than 310-nm wavelength to this coumarin-modified MCM-41 induced the photodimerization of

coumarin to close the pore outlet with cyclobutane dimer. Si analyses of the samples were carried out using ICP

(Shimadzu, ICPV-1017). CHN analyses were obtained on CE instruments EA1110. Crystal structure was

determined by XRD patterns. Specific surface area and pore size were obtained from nitrogen adsorption

isotherms measured at -196 °C. The pore size distributions were calculated from the adsorption branches of the

nitrogen adsorption isotherms using the Barrett-Joyner- Halenda (BJH) method. Thermogravimetric analyses

(TGA) and differential thermal analyses (DTA) were also carried out. UV-vis diffuse reflectance spectra were

recorded. Solid-state 29Si MAS NMR, solution 1H and 13C NMR spectrum measurements were performed to

find the molecular mass and environment of Si, H and C. Presence of functional groups was characterized by

FT-IR spectra measured on a Perkin-Elmer Spectrum One spectrometer. The content of phenanthrene in filtrate

(solution) was analyzed using GC (Shimadzu GC-17A) with a capillary column and independently verified by

elemental analysis and TG. The molecular size estimation was carried out using CS ChemBats3D Pro

(Cambridge Soft Corporation.

In 2003 Corine et al., [28] anchored a non-steroidal anti-inflammatory drug (ibuprofen) inside the

mesoporous channels of MCM-41-type silica and on a silica gel surface through grafting. In 2007, Tomiko M. et

al.,[29] reported the synthesis of new amino-functionalized monodispersed mesoporous silica spheres (MMSS)

directly by co-condensation of 3-aminopropyltrimethoxysilane (AP-TMS), [3-(2-

aminoethylamino)propyl]trimethoxysilane (AEAP-TMS) or 3-[2-(2-

aminoethylamino)ethylamino]propyltrimethoxysilane (AEAEAP-TMS) with tetramethoxysilane. Powder X-ray

diffraction measurements were carried out to find the crystallographic parameters of the produt samples. The

average particle diameter was calculated from Scanning electron micrographs (SEMs) recorded with a SIGMA-

V (Akashi Seisakusho). The standard deviation was also calculated, from which the particle diameter

distribution was judged. The nitrogen adsorption isotherm was measured using a Belsorp-mini II (BEL Japan) at

77 K. The sample was evacuated at 373K under 10−3 mmHg before measurement. The pore diameter was

calculated by using the Barrett–Joyner–Halenda (BJH) method. Specific surface area was calculated by

considering the linearity of a Brunauer–Emmett–Teller (BET) plot. Transmission electron micrographs were

obtained using a JEOL-200CX TEM at an acceleration voltage of 200 kV. 29Si magic-angle-spinning (MAS)

nuclear magnetic resonance (NMR) and 13C cross-polarization (CP) NMRanalyses were carried out on a Bruker

AVANCE 400 spectrometer at 79.49MHz for 29Si and at 100.61MHz for 13C. The 29Si MAS NMR spectra

were measured at 60 s repetition delay and 3_s pulse width. The 13C CP-MAS NMR spectra were measured

with a repetition delay of 2 s, 2 ms contact time, and 2.8_s 1H 90◦ pulse. N elemental analyses (EA) were

carried out on an Elementer varioEL elemental analyzer. Proton conductive inorganic–organic hybrid

membranes were synthesized by Gengjin Kong et al., [30] They used Epoxycyclohexylethyltrimethoxysilane

(EHTMS) and 1-hydroxyethane-1, 1-diphosphonic acid (HEDPA) as starting materials. In this research work,

the effect of gel temperature, membrane-forming temperature and Si/P on hybrid membranes performance were

discussed. FT-IR analysis as well as Thermal analysis of the hybrid membranes prepared at different membrane-

forming temperatures and different ratios of Si/P were recorded. Pham et al. [31] conducted surface

modification on 30nm colloidal silica particles using 3-aminopropyltrimethoxysilane (APTS) and 3-

aminopropyldimethylmethoxysilane (APMS) under aqueous conditions. Through these studies it was

investigated, for an efficient surface modification using the silane coupling agents one must use low

concentrations of silane solution and longer reaction time. Vejayakumaran et al.,[32] reported grafting of amino

group onto ∼7 nm nanosilica in non-aqueous by using APTS. The grafted silica particles were further grafted

with BMI monomer to form Si-BMI nanocomposite via nucleophilic addition. An amino-functionalized

Monodispersed silica[33] with different particle size of 310–780nm has been synthesized by direct

cocondensation of 3-aminopropyltrimethoxysilane (APTMS), [3-(2-aminoethylamino) propyl] trimethoxysilane

(AEAP-TMS), or 3-[2-(2-aminoethylamino) ethylamino] propyltrimethoxysilane (AEAEAPTMS) with

tetramethoxysilane. The functionalized silica particles showed an excellent catalytic activity in the condensation

reactions of nitroaldols. Rahman et al., [20] reported an easy and swift pathway in preparation of amine-

functionalized ∼60nm nanosilica via co condensation method in non-aqueous media using APTS as coupling

agent. Amino-functionalized silica nanoparticles [33] have also been synthesized from precursor mixtures of

tetraethoxysilane and aminopropyltriethoxysilane in ethanol/water solutions via a one-pot sol gel procedure. The

amino-functionalized silica particles have some potential biomedical applications such as carriers of enzymes,

drugs, and DNA.

7. Synthesis and Grafting of ORMOCERS The organometallics of Cu and Ni will be prepared in the inert environment and then these

organometallics will be inserted in Si(OEt)4 as well as organosilanes Vinyltriethoxysilane (VTS),

Methacryloxypropyltriethoxysilane (MPTS), 3-Glycidyloxypropyltrimethoxysilane (GPTS), 3-

Aminopropyltrimethoxysilane (APTS), 3-Mercaptopropyltriethoxysilane (McPTS) and

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Chloropropyltriethoxysilane (CPTS) and NH4F as catalyst separately to obtain Cu and Ni embedded

ORMOCERS. Proposed reaction and structure of the ORMOCERS is as follows:

Condensation,heat,

SiO2, Organometall ic(11)(RO)3SiR

1 + 3H2O (OH)3SiOR

1 + 3ROH

SiO

SiO

MO

SiO

MOHOH

R1

R1 R1

R1

R1

o o o OHo

R1= -NH2, -SH,-OH, = ,etc

Solid samples of these prepared gels will be grinded to a powder and then pyrolysed. There will be two

possible routes for the pyrolysed species. One of the possible way will be grinding and sintering to produce

compact matter and second one will be grafting with amine derivatives of Furfural, Furyacrylic acid, Cinnamic

acid, Pyrrol, Coumarine and Quinoxalin.

8. Future prospects The ORMOCERS based hybrid composites have numerous applications, notably when grafted with

heterocyclic amines. The insertion of organometallic precursors in sol-gel process to get transition metal

embedded ORMOCERS subsequently grafted with heterocylic amines are proposed in this work. Amino

derivatives of Furfural, Furyacrylic acid, Cinnamic acid, Pyrrol, Coumarine and Quinoxalin will be prepared,

characterized and used for grafting with ORMOCERS. These hybrid materials are expected to be optically

active within the visible range. These can be eventually used as optical brighteners and dyes in the textile

industry.

9. Conclusion The main focus of this review article was to discuss the chemistry of sol-gel process as well as

utilization of ORMOCERS. Sol-gel method is quite promising to synthesis Hybrid and Composite materials

under controlled conditions. Composites and Hybrid materials combine both the advantages of organic polymers

(flexibility, lightweight, good impact resistance and process ability, etc.) and inorganic materials (high

mechanical strength, good chemical resistance, thermal stability, etc.). ORMOCERS have reactive organic

groups which are capable of reacting with organic monomers/polymers, thus providing strong bonding between

the organic network and the inorganic lattice, which allows the creation of entirely new generation of advanced

materials like Hybrid and Composite material. The proposed method will help the cause to make low price and

mechanically strong dyes and optical brighteners. Extensive delocalization between the diazo group and

aromatic ring will be the origin of the optical activity of the proposed materials in the visible range.

10. Acknowledgement The work is conducted under the DPI Grant No 02(DPI08)/824/2011(08), Department of Mechanical

and Manufacturing Engineering, Faculty of Engineering, Universiti Malaysia Sarawak (UNIMAS), 94300 Kota

Samarahan, Sarawak, Malaysia.

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