9 Polymeric Composite Films with Controlled Release of Natural Antioxidant Enoxil
151
9.2 Materials and Methods
The Enoxil preparation, developed by the Institute of Chemistry of the Academy
of Sciences of Moldova, is a set of biological polyphenols and served as an
antimicrobial agent. It was obtained by extraction from grape seeds using ethanol
p.a. as a solvent. For increasing the solubility in water, enotannins were chemically
treated with H 2 O 2 , which has led to depolymerization of catechin and epicatechin
oligomers, and, as a result, novel hydrophilic product (Enoxil) has been obtained.
The composite system of nanosized nonporous hydrophilic fumed silica A-300
(specific surface area of 300 m 2 /g, Kalush, Ukraine) with Enoxil was performed
by mixing 3 g of silica with 75 mL of Enoxil aqua solution (8.0 mg/mL). After
impregnation, the composite was dried at 80 ◦ C.
The Enoxil-silica gel composites were prepared by in situ polycondensation
(gelation) of the precursors tetraethoxysilane (TEOS) or mixture of TEOS and
phenyltrimethoxysilane (PhTMS). In a typical process, initially 0.6 g of Enoxil was
dissolved in 15 ml of a mixture (10 ml H 2 O + 5 ml C 2 H 5 OH) at 40 ◦ C under
acidic conditions produced by the addition of 1 mL HCl (0.1 M). A dissolution
was achieved after 1 h of continuous mechanical stirring of the solution. Then,
11 mL TEOS or 5 ml of mixture (2 ml TEOS and 3 ml PhTMS) was added to the
abovementioned solution followed by continuous stirring for another 2 h at 40 ◦ C.
And the solution was remained constant over 12 h to aging of a gel. Thereafter, the
solution was treated at 80 ◦ C for 4 h. After cooling down to room temperature, the
solid products were washed and dried at 70 ◦ C.
Gelatin commercially available and chitosan of low viscosity and deacetylation
degree of 70% (Fluka) were used without addition treatment. The monomers
used 2-hydroxyethyl methacrylate (HEMA), (3-aminopropyl)triethoxysilane, and
triethoxyvinylsilane were purchased from Aldrich with purity ≥99%.
9.2.1 Preparation of Polymeric Composite Films
Various polymers were used to form composite films.
For preparation of gelatin/HEMA (Gel/HEMA) films into the gelatin water
solution were added HEMA and HEMA pretreated with a mixture amino- and
vinylsilane (3-aminopropyl)triethoxysilane and triethoxyvinylsilane) in the 1:1
molar ratio (silica precursor content was 10 wt%) for preparing Gel/HEMA/VA
films.
Gelatin/chitosan films were prepared by a casting solvent evaporation technique.
3 wt % chitosan solution in 1 wt% acetic acid was mixed with 3 wt% gelatin aqueous
solution under stirring at the room temperature. Initial mixture was divided into two
parts, to forming pure (Gel/Chit) and filled with carbon nanotubes (Gel/Chit/NT)
materials. The filling degree was 0.1 wt% MWCN obtained from the Chuiko
Institute of Surface Chemistry of National Academy of Sciences of Ukraine.
151
9.2 Materials and Methods
The Enoxil preparation, developed by the Institute of Chemistry of the Academy
of Sciences of Moldova, is a set of biological polyphenols and served as an
antimicrobial agent. It was obtained by extraction from grape seeds using ethanol
p.a. as a solvent. For increasing the solubility in water, enotannins were chemically
treated with H 2 O 2 , which has led to depolymerization of catechin and epicatechin
oligomers, and, as a result, novel hydrophilic product (Enoxil) has been obtained.
The composite system of nanosized nonporous hydrophilic fumed silica A-300
(specific surface area of 300 m 2 /g, Kalush, Ukraine) with Enoxil was performed
by mixing 3 g of silica with 75 mL of Enoxil aqua solution (8.0 mg/mL). After
impregnation, the composite was dried at 80 ◦ C.
The Enoxil-silica gel composites were prepared by in situ polycondensation
(gelation) of the precursors tetraethoxysilane (TEOS) or mixture of TEOS and
phenyltrimethoxysilane (PhTMS). In a typical process, initially 0.6 g of Enoxil was
dissolved in 15 ml of a mixture (10 ml H 2 O + 5 ml C 2 H 5 OH) at 40 ◦ C under
acidic conditions produced by the addition of 1 mL HCl (0.1 M). A dissolution
was achieved after 1 h of continuous mechanical stirring of the solution. Then,
11 mL TEOS or 5 ml of mixture (2 ml TEOS and 3 ml PhTMS) was added to the
abovementioned solution followed by continuous stirring for another 2 h at 40 ◦ C.
And the solution was remained constant over 12 h to aging of a gel. Thereafter, the
solution was treated at 80 ◦ C for 4 h. After cooling down to room temperature, the
solid products were washed and dried at 70 ◦ C.
Gelatin commercially available and chitosan of low viscosity and deacetylation
degree of 70% (Fluka) were used without addition treatment. The monomers
used 2-hydroxyethyl methacrylate (HEMA), (3-aminopropyl)triethoxysilane, and
triethoxyvinylsilane were purchased from Aldrich with purity ≥99%.
9.2.1 Preparation of Polymeric Composite Films
Various polymers were used to form composite films.
For preparation of gelatin/HEMA (Gel/HEMA) films into the gelatin water
solution were added HEMA and HEMA pretreated with a mixture amino- and
vinylsilane (3-aminopropyl)triethoxysilane and triethoxyvinylsilane) in the 1:1
molar ratio (silica precursor content was 10 wt%) for preparing Gel/HEMA/VA
films.
Gelatin/chitosan films were prepared by a casting solvent evaporation technique.
3 wt % chitosan solution in 1 wt% acetic acid was mixed with 3 wt% gelatin aqueous
solution under stirring at the room temperature. Initial mixture was divided into two
parts, to forming pure (Gel/Chit) and filled with carbon nanotubes (Gel/Chit/NT)
materials. The filling degree was 0.1 wt% MWCN obtained from the Chuiko
Institute of Surface Chemistry of National Academy of Sciences of Ukraine.