J. Mindemark, T. Bowden / Polymer 52 (2011) 5716e5722
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2. Materials and methods
2.4. Synthesis of 3-ethyl-3-hydroxymethyloxetane
2.1. Materials
93.9 g (0.700 mol) of trimethylolpropane, 85 ml (0.70 mol) of
diethyl carbonate and 400 mg (2.9 mmol) of K2CO3 were stirred and
heated in a 250 ml round-bottom flask. At 110 ꢀC a clear solution
was formed and at 130 ꢀC ethanol started to distil off. The pressure
was gradually reduced to distil off all of the ethanol formed in the
reaction as well as any residual diethyl carbonate. The temperature
was increased and at 195 ꢀC the product was distilled off under
reduced pressure. Yield: 58.4 g (72%) as a clear liquid, bp
122e127 ꢀC/40 mbar (litt. bp 84 ꢀC/2.8 Torr [28]). 1H NMR
Trimethylene carbonate (Boehringer Ingelheim) and tin(II) 2-
ethylhexanoate (Alfa Aesar) were handled and stored in a glove
box and used as received. Chloroform-d was purchased from Lar-
odan Fine Chemicals and stored over 4 Å molecular sieves and solid
K2CO3. DMSO-d6 was purchased from Larodan Fine Chemicals and
stored over 3 Å molecular sieves. All other chemicals, including dry
dichloromethane (Acros Organics), were obtained from commercial
sources and used as received.
(400 MHz, DMSO-d6, ppm):
d
¼ 0.82 (t, 3H, J ¼ 7.4 Hz, eCH3), 1.62
(q, 2H, J ¼ 7.4 Hz, eCH2e), 3.50 (d, 2H, J ¼ 5.4 Hz, eCH2eOH), 4.19
(d, 2H, J ¼ 5.6 Hz, eCH2eO), 4.29 (d, 2H, J ¼ 5.6 Hz, eCH2eO), 4.78
(t, 1H, J ¼ 5.4 Hz, eOH).
2.2. Characterization
1H and 13C NMR spectra were recorded at 25 ꢀC on a JEOL
Eclipseþ 400 MHz NMR spectrometer using the residual solvent
signal as an internal standard. Quantitative 13C NMR experiments
were run using inverse gated decoupling and a relaxation delay of
4 s, assuming equal relaxation times for all carbonyl carbon nuclei.
Deconvolution using Lorentzian lineshapes was used to obtain the
integrals.
Melting points and glass transition temperatures were deter-
mined using differential scanning calorimetry on a TA Instruments
DSC Q1000. Melting points for low-molecular-weight compounds
were obtained as the onset of the melting endotherm at a heating
rate of 0.5 ꢀC/min and the purity (mol%) was estimated using purity
analysis in Universal Analysis 2000 version 4.7A (TA Instruments).
Any endotherms at higher temperatures were disregarded. Poly-
mer samples were heated to 180 ꢀC at a rate of 10 ꢀC/min and then
quenched to ꢁ60 ꢀC to erase the thermal history, followed by
a heating scan to 180 ꢀC at a rate of 10 ꢀC/min for measurement.
Polymer crystallization and melting points are reported as the peak
maxima, or the range thereof, of the crystallization exotherm and
melting endotherm(s), respectively.
Polymer degradation was measured using thermogravimetric
analysis on a TA Instruments TGA Q500. Samples were heated at
a rate of 10 ꢀC/min to 500 ꢀC under a nitrogen atmosphere and the
decomposition temperature (Td) was determined as the onset of
degradation.
Determination of molecular weights through GPC was per-
formed on a Verotech PL-GPC 50 equipped with a refractive index
detector and two PolarGel-M organic GPC columns. Samples were
injected using a PL-AS RT autosampler and chloroform was used as
the eluent at a flow rate of 1 ml/min. Flow rate fluctuations were
corrected by an internal standard and the system was calibrated
against narrow polystyrene standards.
2.5. General procedure for the synthesis of 2-(halomethyl)-2-alkyl-
1,3-propanediols
A solution of 3-alkyl-3-hydroxymethyloxetane (100 mmol) in
100 ml of THF was stirred and cooled in an ice bath. Aqueous
mineral acid (25 ml of conc. HCl or 34 ml of conc. HBr, respectively)
was added dropwise. The ice bath was removed and the reaction
was allowed to proceed at r.t. overnight. The solution was
neutralized with 250 ml of saturated NaHCO3 and was extracted
with 3 ꢂ 200 ml of diethyl ether. The organic phases were retained,
dried with MgSO4 and the solvent was evaporated. The crude
products were recrystallized from toluene.
2.5.1. Synthesis of 2-(chloromethyl)-2-methyl-1,3-propanediol
Yield: 11.2 g (81%) as white needles, mp 58.1 ꢀC (99.8% purity).
Litt. mp 79e80 ꢀC [29]. 1H NMR (400 MHz, DMSO-d6, ppm):
d
¼ 0.83 (s, 3H, eCH3), 3.27 (m, 4H, eCH2eOH), 3.53 (s, 2H,
eCH2eCl), 4.56 (t, 2H, J ¼ 5.3 Hz, eOH). 13C NMR (100 MHz, CDCl3,
ppm):
d
¼
17.6 (eCH3), 41.4 (>C<), 49.0 (eCH2eCl), 68.0
(eCH2eOH). Anal. calcd for C5H11ClO2: C, 43.33; H, 8.00; Cl, 25.58.
Found: C, 43.37; H, 7.72; Cl, 25.40.
2.5.2. Synthesis of 2-(chloromethyl)-2-ethyl-1,3-propanediol
Yield: 13.6 g (89%) as white flakes, mp 63.7 ꢀC (99.8% purity).
Litt. mp 62e63 ꢀC [29]. 1H NMR (400 MHz, DMSO-d6, ppm):
d
¼ 0.81 (t, 3H, J ¼ 7.5 Hz, eCH3),1.27 (q, 2H, J ¼ 7.5 Hz, eCH2e), 3.26
(d, 4H, J ¼ 5.1 Hz, eCH2eOH), 3.51 (s, 2H, eCH2eCl), 4.49 (t, 2H,
J ¼ 5.1 Hz, eOH). 13C NMR (100 MHz, CDCl3, ppm):
d
¼ 7.3 (eCH3),
22.8 (eCH2e), 43.6 (>C<), 46.4 (eCH2eCl), 66.3 (eCH2eOH). Anal.
calcd for C6H13ClO2: C, 47.22; H, 8.59; Cl, 23.23. Found: C, 47.23; H,
8.36; Cl, 23.48.
Elemental analyses were performed by Analytische Laborator-
ien, Lindlar, Germany.
2.5.3. Synthesis of 2-(bromomethyl)-2-methyl-1,3-propanediol
Yield: 14.8 g (81%) as white needles, mp 70.7 ꢀC (99.8% purity).
2.3. Synthesis of 3-methyl-3-hydroxymethyloxetane
Litt. mp 72e73 ꢀC [29]. 1H NMR (400 MHz, DMSO-d6, ppm):
d
¼ 0.86
(s, 3H, eCH3), 3.28 (m, 4H, eCH2eOH), 3.46 (s, 2H, eCH2eBr), 4.58
84.1 g (0.700 mol) of trimethylolethane, 85 ml (0.70 mol) of
diethyl carbonate and 400 mg (2.9 mmol) of K2CO3 were stirred and
heated in a 250 ml round-bottom flask. At 130 ꢀC a clear solution
was formed and ethanol started to distil off. The pressure was
gradually reduced to distil off all of the ethanol formed in the
reaction as well as any residual diethyl carbonate. The temperature
was increased to 200 ꢀC and the product was distilled off under
reduced pressure. Yield: 44.7 g (63%) as a clear liquid, bp
123e129 ꢀC/100 mbar (litt. bp 80 ꢀC/4 Torr [28]). 1H NMR (400 MHz,
(t, 2H, J ¼ 5.3 Hz, eOH). 13C NMR (100 MHz, CDCl3, ppm):
d
¼ 18.6
(eCH3), 39.4 (eCH2eBr), 40.8 (>C<), 68.4 (eCH2eOH). Anal. calcd
for C5H11BrO2: C, 32.81; H, 6.06; Br, 43.65. Found: C, 32.78; H, 6.03;
Br, 41.70.
2.5.4. Synthesis of 2-(bromomethyl)-2-ethyl-1,3-propanediol
Yield: 16.0 g (81%) as white flakes, mp 79.9 ꢀC (99.7% purity).
Litt. mp 80e81 ꢀC [29]. 1H NMR (400 MHz, DMSO-d6, ppm):
d
¼ 0.80 (t, 3H, J ¼ 7.5 Hz, eCH3),1.27 (q, 2H, J ¼ 7.5 Hz, eCH2e), 3.26
DMSO-d6, ppm):
d
¼ 1.18 (s, 3H, eCH3), 3.43 (d, 2H, J ¼ 5.5 Hz,
(d, 4H, J ¼ 5.1 Hz, eCH2eOH), 3.43 (s, 2H, eCH2eBr), 4.51 (t, 2H,
eCH2eOH), 4.15 (d, 2H, J ¼ 5.5 Hz, eCH2eO), 4.35 (d, 2H, J ¼ 5.5 Hz,
J ¼ 5.1 Hz, eOH). 13C NMR (100 MHz, CDCl3, ppm):
d
¼ 7.3 (eCH3),
eCH2eO), 4.84 (t, 1H, J ¼ 5.5 Hz, eOH).
23.6 (eCH2e), 36.8 (eCH2eBr), 42.9 (>C<), 66.6 (eCH2eOH). Anal.