Conventional (Uracil-1): Propiolic acid (5 g) was added to stirred solution of urea (4.3g) and anhydrous benzene (120 mL) at 25C.
Microwave (Uracil-II): urea (1.1g) and anhydrous benzene (6.0 mL) were stirred at room temperature and propiolic acid (1.3mL) and concentrated sulphuric acid (1-2 drops) were added to it.
(Uracil-III): The mixture of urea (1.1g), propiolic acid (1.5g) and conc.sulphuric acid (2-3 drops) was subjected to microwave radiation for 20 seconds.
U-I and U-II which were synthesized by the condensation of propiolic acid and urea in presence of benzene (Subbaraman et al,1980) showing molecular ion peak at m/z=112 corresponding to molecular formula C4H4N2O2.
Poly(ethylene glycol) methyl ether acrylate (PEGMA, [M.sub.n] = 480g/mol, Aldrich) was passed through basic alumina column to remove the inhibitor Ethyl [alpha]-bromoisobutyrate (EBIB, 98%, Aldrich), 2,3,4,5,6-pentafluorobenzyl chloride (Aldrich 99%), CuCl ([greater than or equal to] 99.99%, Aldrich), CuBr (98%, Aldrich), sodium azide (Na[N.sub.3], Sigma-Aldrich), 2,2-bipyridine (bpy, 99%, Fluka), N, N, N', N", N" -pentamethyldiethylenetriamine (PMDETA, 99%, Aldrich), methanol ([greater than or equal to] 99.9, Aldrich), N, NThicyclohexylcarbodiimide (DCC, 99%, Aldrich), 4-(dimethylamino) pyridine (DMAP, [greater than or equal to] 99.99%, Aldrich), propiolic acid (99%, Aldrich), and N, N-dimethylformamide (DMF, 99%, Aldrich) were used as received.
To obtain alkyne-P(HEMA-co-MMA)block-PPEGMA (3b, 3d), P(HEMA-co-MMA)-block-PPEGMA (2b, 2d) (0.5 g, 0.008 mmol), DCC (0.053 g, 0.256 mmol), DMAP (0.003 g, 0.0256 mmol), and propiolic acid (0.017 g, 0.24 mmol) were added in a round-bottom flask and dissolved in 50 mL C[H.sub.2][Cl.sub.2] under stirring at room temperature.
Finally, propargyl moieties were introduced via the Steglich esterification between the hydroxyl side-functionalities of HEMA and propiolic acid.
Propargyl side-functional block copolymers, alkyneP(HEMA-co-MMA)-block-PPEGMA (3b and 3d), were prepared by the Steglich esterification between hydroxyl groups of HEMA and propiolic acid in the presence of DCC and DMAP at room temperature .