monomer), and initiated by TMP (6.94 mmol; 0.93 g) at
130
C for 48 h under an argon atmosphere.
4. The monomer conversion and the degree of polymerization
can be determined by
1 H-NMR spectroscopy using CDCl 3 as a
solvent. Assuming that each hydroxyl group of the glycerol
initiates polymerization of TMC, the degree of polymerization
is determined by comparing the peak integral that characterizes
the -CH 2 - groups of the TMC at 4.2 ppm (4H) or 2.05 ppm
(2H) with the CH 3 - groups from the TMP initiator at 0.8 ppm
(3H). Monomer conversion is calculated from the peak integral
of the PTMC at 4.2 ppm (4H) or 2.05 ppm (2H) compared to
the peak integral of the TMC monomer at 4.4 ppm (4H) or
2.2 ppm (2H).
5. Same characterization and efficacy are obtained with PDLLA
oligomers. The conversion is determined by the characteristic
peak integral of lactide monomers at 5.05 ppm corresponding
to the -CH- (1H) groups and the peak integral of the -CHfrom PDLLA at 5.15 ppm. Conversion rate for both polymer
types is traditionally close to 95–99%.
3.2 Preparation
of the Photosensitive
Resin Precursor
Following the synthesis of the hydroxy-terminated oligomers, the
next step of the resin preparation consists of the
end-functionalization of the oligomers by photosensitive groups
able to polymerize under light initiation. This functionalization is a
key step to achieve a photocrosslinkable resin. The most straightforward approach of such functionalization is to end-cap the polymer chains through the reaction of the hydroxyl end-groups with
photoreactive acrylate or methacrylate groups in order to induce
radical photopolymerization [16], which leads to photosensitive
macromers. Radical photopolymerization is a fast, selective, and
highly effective reaction, which is a crucial requirement in SL. In
conventional SL technology, the resin composition includes the
photosensitive polymer resin, a photoinitiator, and if necessary an
inert or reactive diluent.
1. After dissolution of the hydroxy-terminated oligomers in anhydrous dichloromethane (100 mL) (see Note 3), add an excess
of anhydrous methacrylic anhydride (0.15 mol; 22 mL) in the
presence of triethylamine (0.15 mol; 20 mL). The reaction is
performed at room temperature under stirring and argon
atmosphere for 3 days.
2. Purify photosensitive resin by precipitation (see Note 4). Dispense the resin dropwise in 500 mL of ice-cold methanol inside
a beaker under vigorous stirring. Recover and vacuum-dry the
precipitate. A sticky white paste should be obtained.
3. The degree of functionalization can be determined by
1 H-NMR analysis in CDCl 3 . Taking into account the degree
TPMS Scaffolds by Stereolithography
23
130
C for 48 h under an argon atmosphere.
4. The monomer conversion and the degree of polymerization
can be determined by
1 H-NMR spectroscopy using CDCl 3 as a
solvent. Assuming that each hydroxyl group of the glycerol
initiates polymerization of TMC, the degree of polymerization
is determined by comparing the peak integral that characterizes
the -CH 2 - groups of the TMC at 4.2 ppm (4H) or 2.05 ppm
(2H) with the CH 3 - groups from the TMP initiator at 0.8 ppm
(3H). Monomer conversion is calculated from the peak integral
of the PTMC at 4.2 ppm (4H) or 2.05 ppm (2H) compared to
the peak integral of the TMC monomer at 4.4 ppm (4H) or
2.2 ppm (2H).
5. Same characterization and efficacy are obtained with PDLLA
oligomers. The conversion is determined by the characteristic
peak integral of lactide monomers at 5.05 ppm corresponding
to the -CH- (1H) groups and the peak integral of the -CHfrom PDLLA at 5.15 ppm. Conversion rate for both polymer
types is traditionally close to 95–99%.
3.2 Preparation
of the Photosensitive
Resin Precursor
Following the synthesis of the hydroxy-terminated oligomers, the
next step of the resin preparation consists of the
end-functionalization of the oligomers by photosensitive groups
able to polymerize under light initiation. This functionalization is a
key step to achieve a photocrosslinkable resin. The most straightforward approach of such functionalization is to end-cap the polymer chains through the reaction of the hydroxyl end-groups with
photoreactive acrylate or methacrylate groups in order to induce
radical photopolymerization [16], which leads to photosensitive
macromers. Radical photopolymerization is a fast, selective, and
highly effective reaction, which is a crucial requirement in SL. In
conventional SL technology, the resin composition includes the
photosensitive polymer resin, a photoinitiator, and if necessary an
inert or reactive diluent.
1. After dissolution of the hydroxy-terminated oligomers in anhydrous dichloromethane (100 mL) (see Note 3), add an excess
of anhydrous methacrylic anhydride (0.15 mol; 22 mL) in the
presence of triethylamine (0.15 mol; 20 mL). The reaction is
performed at room temperature under stirring and argon
atmosphere for 3 days.
2. Purify photosensitive resin by precipitation (see Note 4). Dispense the resin dropwise in 500 mL of ice-cold methanol inside
a beaker under vigorous stirring. Recover and vacuum-dry the
precipitate. A sticky white paste should be obtained.
3. The degree of functionalization can be determined by
1 H-NMR analysis in CDCl 3 . Taking into account the degree
TPMS Scaffolds by Stereolithography
23