Supplementary File
Thermally induced fixed diradical generation on solid supports for surface initiated
polymerization
Baris Gure, Niyazi Bicak*
Istanbul Technical University, Department of Chemistry, Maslak 34469 Istanbul-Turkey
Experimental
Materials
Methacryloyl chloride (Aldrich), anhydrous potassium carbonate (E. Merck), methyl isobutyl
ketone
(Aldrich)
and
poly(N-vinyl
pyrrolidinone)
were
used
as
purchased.
Methylmethacrylate (MMA), styrene, N-vinyl formamide (NVF), N-vinyl pyrrolidinone,
(NVP), acrylonitrile, vinyl acetate (Vac), and ethanolamine were distilled prior to use. The
solvent, 1,4-dioxane (Aldrich) was redistilled over P2O5 before use.
Characterizations
FT-IR spectra were taken by a Perkin Elmer FT-IR Spectrum One B spectrometer.
1H-NMR
spectra were recorded in CDCl3 solvent using a Bruker 250 MHz NMR
spectrometer.
13C-NMR
spectra were recorded at 75 MHz using Varian Mercury plus 300 MHz
spectrometer in CDCl3 solvent.
Thermogravimetric analysis (TGA) of the microbeads was carried out using Perkin Elmer
Diamond TG/DTA under nitrogen atmosphere at a heating rate of 10 oC per minute.
Differential scanning calorimetry (DSC) trace of nitrosoated microbeads were taken by
Perkin Elmer (DSC4000) under nitrogen atmosphere. The rate of heating was 10 oC / min.
UV-Vis spectra were obtained by a Chebios Optimum-One UV–visible spectrophotometer.
Scanning Electron Microscopy (SEM) pictures were taken using JEOL JSM-6335F at
TUBITAK MAM laboratory in Gebze.
Synthesis of Methacryloyloxyethyl Methacrylamide (METAM):
Methacryloyl chloride (14 mL, 0.14 mol), anhydrous potassium carbonate (20 g, 0.145 mol),
1 mL methyl isobutyl ketone (as polymerization inhibitor) and 30 mL of dry 1,4-dioxan were
placed in a 250 mL round bottom flask mounted in an ice bath. The flask was equipped with a
reflux condenser and a dropping funnel. A solution of 4 mL ethanolamine (0.065 mol) in 15
mL 1,4-dioxan was added drop wise to the mixture through the dropping funnel in 15-20 min,
while stirring. This mixture was heated at 90 oC for 4 h. The mixture was cooled and filtered
to remove solid potassium carbonate. The solvent was removed by rotary evaporator. The
residue wad dissolved in 50 mL ethyl acetate. The solution was shaken with 100 mL of icecold Na2CO3 solution and 100 mL distilled water. The organic layer was dried with anhydrous
Na2SO4 and chromatographed through a short silicagel column (1×15 cm). After removal of
ethyl acetate, the product was isolated as light yellow liquid. The yield was 10.3 g (80.4 %).
1
H-NMR spectrum of the product revealed highly pure Methacryloyloxyethyl methacrylamide
(METAM) structure. The product was used without further purification.
Characterization of Methacryloyloxyethyl Methacrylamide (METAM):
The amide functional crosslinker, METAM was synthesized by action of metharyloylchloride
on ethanolamine in the presence of solid K2CO3 as acid scavenger (Scheme-S1). The oily
product isolated is light yellow in color and immiscible with water. Recently a slightly
different procedure has been reported for the synthesis of this compound19.
Scheme-S1: Synthesis of the amide functional crosslinker, METAM.
1
HNMR spectrum of this product (Fig-S1) clearly shows methacryloyloxymethacrylamide
(METAM) structure. Thus, proton signals of –OCH2- and –NH-CO groups appear at 4.01 and
3.7 ppm respectively.
Figure-S1: 1HNMR spectrum of METAM monomer (in CDCl3)
The strong singlet at 1.7 ppm represents methyl group protons of the two methacrylate
functions.
Methylenic cis- and trans- protons of the metacrylate ester group represent two singlets at 5.8
and 5.3 ppm respectively. The signals appeared at 5.5 and ppm 5.0 is associated with
methylene protons of the methacrylamide group in cis- and trans-positions respectively.
Figure-S2: FT-IR spectrum of METAM monomer.
Methacryloyloxyethylmethacrylamide (METAM) structure of this product is confirmed also
by the FT-IR spectrum. A characteristic carbonyl group vibration of the methacrylate ester
function appears at 1720 cm-1. The broad band centered at 1680 cm-1 must be due to
combination of N-H plane bending and carbonyl vibration of methacrylamide function.
Stretching vibration of C=C bond represents a sharp peak at 1650 cm-1. The sharp peaks
observed at 1230 and 1150 cm-1 are associated with C-N and C-O vibrations.
13
CNMR spectrum of METAM in Fig-S3 shows all the carbon signals. Thus, the signals of
the carbonyl carbons appear 169 and 168 ppm. Tertiary carbons of methacryl ester and amide
units represent weak signals at 140 and 136 ppm respectively. Terminal carbons of
methacrylate double bonds involved in methacryamide and in methacryate ester groups give
strong signals at 127 and 121 ppm respectively. Methyl group carbons show
a nearly
combined singlet around 19 ppm. The magnified image reveals two distinct signals at 19 and
18.6 ppm. The signals at 64 and 39ppm are associated with carbon atoms of ethylene bridge,
the later being connected to the nitrogen atom. The figure shows no satellite signal implying
purity of this compound.
Figure-S3: 13 CNMR spectrum of METAM in CDCl3.
Determination of the nitrosoamide content of the microspheres :
To determine the nitrosoamide content of the nitrosated PMMA-METAM microbeads, first we
studied iodometric method reported by Stedronsky et al 22. However, the procedure given did not
work in our hands, probably due to side reaction of iodine with the polymer. An alternative
colorimetric method used for analysis of nitrite ion20 was adopted for the determination of
nitrosoamide content, in which a weighed amount of bead sample was treated with acidified THF
solution of 2,7 dihydroxy naphthalene (2,0 %) and the nitrosoamide content was assayed
colorimetrically, based on the absorption maxima of the red compound, 1-nitroso 2,7-dihydroxy
naphthalene at 480 nm. In this procedure, 0.10 g bead sample was mixed with THF solution of
dihydroxy naphthalene (10 mL) and 1 mL HCl solution (37 %) and stirred for 24 h in a tightly
closed bottle. Correlation of its absorbance at 480 nm with the calibration curve revealed a
nitrosoamide content of 0.31 ± 0.02 mmol per gram.