Synthetic Copolymer with a Schiff Base
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N-(2-Hydroxypropyl)methacrylamide (I)
A solution of methacryloyl chloride (100 g, 0.96 mol) in acetonitrile (406 ml) stabilized with 2,5-di-
tert-butylhydroquinone (4 mg) was added to a stirred solution of 1-amino-2-propanol (144 g,
1.92 mol) in acetonitrile (376 ml) at −15 °C in 15 min. The mixture was warmed up to 20 °C and
stirred for another 15 min, and the precipitated 1-amino-2-propanol hydrochloride was filtered off.
The product was isolated by cooling the solution to −40 °C, purified by crystallization from the
methanol–diethyl ether 1 : 3 mixture and recrystallization from acetone. Yield 52 g (38%), m.p.
68 – 69 °C (ref.10, m.p. 65 – 68 °C).
N-[N-(N-Methacryloylglycyl)glycyl]-N′-tert-butyloxycarbonylhexane-1,6-diamine (II)
Compound II was prepared by a modification of the procedure developed in ref.11 for the synthesis
of derivatives of N-methacryloylglycylglycine (III). Methacryloyl chloride (8.7 g, 83 mmol) in di-
chloromethane (20 ml) was subjected to the Schotten–Baumann reaction with glycylglycine (11.7 g,
89 mmol) in 15% NaOH (50 ml, 188 mmol) to yield 11.3 g (68%, 57 mmol) of III, which was
transformed into the corresponding p-nitrophenyl ester (IV) by reaction with p-nitrophenol (8.6 g,
62 mmol) in DMF (100 ml) in the presence of N,N′-dicyclohexylcarbodiimide (12.8 g, 61 mmol).
Subsequently, triethylamine (1.3 ml, 9.5 mmol) divided into three equivalent portions was added
(in 10 min intervals) to a stirred solution of IV (3 g, 9.3 mmol) and N-tert-butyloxycarbonyl-1,6-
diaminohexane hydrochloride (2.4 g, 9.5 mmol) in DMF (15 ml), and the mixture was stirred at
20 °C for another 3 h. The precipitated triethylamine hydrochloride was filtered off, the filtrate was
evaporated in a vacuum, and the crude compound II was triturated with diethyl ether and dissolved
in chloroform (15 ml). The solution was extracted with water (3 × 10 ml), dried with MgSO4, and
evaporated. The residue was recrystallized from chloroform–diethyl ether to yield 1.98 g (54%) of II,
m.p. 111 °C, TLC (silica gel, Merck 60F254): RF = 0.61, methanol. For C19H34O5N4 (398.5) calcu-
lated: 57.27% C, 8.60% H, 14.06% N; found: 57.37% C, 8.80% H, 13.97% N.
Poly[N-(2-hydroxypropyl)methacrylamide]
A solution of amide I (3 g, 21 mmol) and AIBN (0.38 g) in methanol (21.6 g) was polymerized in a
sealed glass ampoule under nitrogen at 60 °C for 24 h. The product was precipitated by pouring the
solution into a twentyfold excess of acetone, washed with acetone and diethyl ether, and dried. Yield
of the homopolymer 2 g (67%).
Copolymer with a Schiff Base in Pendant Groups
Poly(I–co–II) was prepared by copolymerization of I (3 g, 21 mmol) with II (1.47 g, 3.7 mmol) in-
duced by AIBN (0.56 g) in methanol (32.2 g) in the same way as the homopolymer; yield 2.5 g
(56%). To remove the terminal tert-butyloxycarbonyl groups of type II monomeric units, the product
was dissolved in methanol (10 ml), mixed with methanolic HCl (20%, 20 ml), and stirred at 20 °C
for 1 h. The copolymer was precipitated with acetone and dried, dissolved in water, and neutralized
with NaHCO3 (pH ca 8.5). The solution was purified by dialysis, and the copolymer with free NH2
end groups was isolated by lyophilization. The amino end groups were transformed into Schiff bases
by reaction with glycolaldehyde (a sixfold molar excess with respect to NH2) in a phosphate buffer
at pH 7 (37 °C, 48 h).
Collect. Czech. Chem. Commun. (Vol. 60) (1995)