PEGylated dendrimer polystyrene support
949
Micro scale suspension polymerization of PS-AHMA
resin
and deposit as yellow crystals. The unreacted materials
were filtered off, washed well with water to remove the
crystalline compound and then with dioxane (5 9 10 mL)
and transferred to solvent extraction apparatus. After
extraction with dioxane for 48 h, the Schiff base resin was
collected, washed with ether (5 9 10 mL) and dried in
40 °C under vacuum. The yield of resin collected was
2.48 g.
Destabilized monomer (styrene, 96 mol %, 10.99 mL) and
cross-linker (AHMA, 4 mol %, 0.752 mL) were mixed
with porogen toluene (8 mL) and radical initiator benzoyl
peroxide (0.5 g) was dissolved in it. The mixture was
suspended in a PVA stabilizer solution (Mn * 70,000,
110 mL) at 90 °C and stirred at a rate of 1,400 rpm for 8 h
under a stream of N2 gas. The mixture was cooled to room
temperature and the polymeric products formed were col-
lected by filtration. The collected bead polymer was con-
tinuously washed with hot water (50 9 50 mL) followed
by solvent extraction with toluene, DCM and MeOH, and
dried to a constant mass. The mesh size 100–200 was
collected and used for further studies.
Diethylene triamine (Dien) resin
The Schiff base G1 resin (2 g) was allowed to stir with HCl
(6 M, 100 mL) at 70 °C for 12 h. The liberated benzal-
dehyde forms an oily emulsion during the hydrolysis and
yellow polymer beads obtained were the hydrochloride
form of the resin, which were filtered off, washed with
ethanol, ether, and dried under vacuum. The amine resin
formed was suspended in 0.5 M sodium hydroxide solution
(50 mL) followed by thorough washing with water until the
solution was turned neutral. Dried well and the free amino
groups formed were qualitatively analyzed by positive
ninhydrin test. The free amino groups formed were quan-
titatively analyzed by acylation with Fmoc-Gly-OH fol-
lowed by measurement of UV absorbance of the adduct
dibenzofulvene:piperidine formed at 290 nm. The amino
loading obtained was 0.495 mmol/g.
PS-AHMA-Chloro resin
4 mol % PS-AHMA resin (0.252 mmol/g, 4 g) was
allowed to swell in distilled DCM (100 mL) for 1 h. The
excess DCM was filtered off and SOCl2 (0.733 mL,
10 mmol excess) reagent was added at 55 °C in dropwise
manner with occasional swirling. After 3 h, the resin was
filtered off, washed with DCM, DMF, dioxane, ethanol,
and methanol (10 9 30 mL each), and dried in vacuum.
The amount of chlorine replaced was quantified by stan-
dard Volhard’s method and obtained as 0.249 mmol/g.
Diazotisation reaction
Schiff base dendrimer (G1) synthesis
The amino G1 resin (2 g, 0.495 mmol/g) was taken in a
R.B flask and added 2 M HCl (20 mL) and kept at 0 °C for
15 min stirring. To this resin, 5 M sodium nitrite solution
(30 mL) was added in dropwise manner with constant
stirring. After the addition of sodium nitrite solution, the
reaction was allowed to stand for 1 h in cold condition and
brought back to room temperature. The hydroxyl resin
beads were washed with excess hot water (5 9 10 mL),
2 M NaOH solution (3 9 10 mL), ethanol (5 9 10 mL),
methanol (5 9 10 mL), and ether (5 9 10 mL) and qual-
itatively checked by negative ninhydrin test. The hydroxyl
groups formed were quantitatively analyzed by esterifica-
tion with Fmoc-Gly-OH and UV absorbance measurements
at 290 nm. It was further confirmed by volumetric esti-
mation of free acetic acid molecules formed by reaction
with acetic anhydride. Both methods gave concordant
value of 0.494 mmol/g.
Bis[2-(Benzaldeneamino)ethyl]amine synthesis
The Schiff base ligand was formed by dissolving one
molecular equivalent of dien (1.061 mL, 10 mmol) with
two molecular equivalent of benzaldehyde (2.0312 mL,
20 mmol) in absolute ethanol at room temperature. After
1 h stirring, the volume of the solution has been reduced,
rotor evaporated and used for reaction without further
1
purification. The formation of ligand was analyzed by H
1
NMR. H-NMR (400 MHz, CDCl3) d = 2.0 (s, 1H,–NH),
d = 2.91 (t, 4H, –CH2, J = 7.1 MHz) d = 3.6 (t, 4H, –
CH2, J = 7.1 MHz), d = 7.5 (m, 4H, J = 7.5 MHz),
d = 7.8 (m, 6H, J = 7.5 MHz), d = 8.65 (s, 2H, = CH).
Schiff base incorporation
(e) Hydroxyl to chloro groups: Hydroxyl resin (2 g,
0.494 mmol/g) was suspended in double-distilled DCM
(25 mL) and allowed to swell for 1 h. The excess solvent
was filtered off and thionyl chloride (73 lL each, 10 mmol
excess) has been added in dropwise with occasional
swirling and kept at 55 °C for an overnight reaction. The
reaction mixture was successively washed with DCM
To the pre-swelled PS-AHMA-Chloro (G0) resin (2 g,
0.249 mmol/g) in 1,4-dioxane, suspension of bis[2-(Benz-
aldeneamino)ethyl]amine Schiff base (2.32 mL, 40 mmol)
was added with trimethylamine (0.5 mL) and heated at
100 °C for 24 h with occasional swirling. The excess
Schiff base ligands act as an acceptor of hydrogen chloride
123