P.S. Bhadury et al. / Journal of Fluorine Chemistry 126 (2005) 1252–1256
1255
coating for piezoelectric sorption detectors. The monomer
and the corresponding polymer fluorosiloxane are capable
of detecting toxic organic vapours, e.g. phosphrous esters.
4. Experimental
Reactions were monitored by GC/MS and the mass
spectra were recorded on a TSQ 7000 mass spectrometer
(Finigan MAT, USA) using a Varian 3400 GC inlet with a
BP-5 column [30 m ꢁ 2.5 m (i.d.) ꢁ 0.25 mm (film thick-
ness)], with a temperature program of 50 8C (2 min)–@
10 8C/min–280 8C (5 min), using helium as carrier gas at a
flow rate of 1.2 ml/min. The injector temperature was
250 8C and transfer line was heated to 280 8C. EI–MS was
performed at 70 eV with the ion-source temperature
180 8C and an emission current of 500 mA. Derivatizing
agent N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA)
Fig. 2. DMMP vapour sorption in interface materials.
observed that after 30 min, Si–H signal disappeared
indicating complete conversion into fluorosiloxane polymer
(Fig. 1).
The formation of fluorinated siloxane was also confirmed
through 1H NMR by observing the disappearance of signals
characteristic to Si–H proton (d 4.72 ppm) of 1,1,3,3,5,5-
hexamethyltrisiloxane and those of allylic group of protons
of monomer (III). Polymer (IV) has been completely
characterized (cf. experimental).
1
was obtained from Lancaster. The H NMR spectra were
recorded on a Bruker Avance DPX-400 spectrometer in
CDCl3 solution, using TMS as internal reference. 19F NMR
was recorded on the same instrument using CFCl3 as
internal standard. IR spectra were recorded on a Nicolet
FT–IR 410 spectrophotometer. The number-average
and weight-average molecular weight of the polymer
was determined using Gel Permeation Chromatograph
(Waters), using tetrahydrofuran (THF) as a solvent.
The inherent viscosity of 1% solution of the polymer in
THF at 32 ꢂ 1 8C was determined using Ubbelhode
viscometer. N,N-dimethylformamide was dried by storing
It should be noted that though the polymer (IV) is well
known for its sensing efficacy [3], we observed that the
monomer (III) itself has an appreciable sorption of DMMP
and may be equally effective for the purpose of sensing
basic vapours. Moreover, it is highly stable and no aging
was noticed even after two and half years. In order to study
static sorption of DMMP in (III) and (IV), the test
materials were placed at 25 8C in a closed chamber
containing a saturated atmosphere of DMMP vapours. The
uptake of the vapours was monitored gravimetrically as per
the reported method [12]. The degree of sorption was
normalized with respect to polyethylene maleate (PEM), a
well-known interface material [1–3]. An organometallic
compound, namely copperbutyrate ethylenediamine (Cu
complex) was also chosen as a reference. It is observed
from Fig. 2 that the monomer (III) (labeled as BSP3-M), as
well as the corresponding fluorosiloxane (IV) (coded as
BSP3-P) has a higher degree of sorption of DMMP as
compared to PEM and the Cu complex. The degree of
sorption for PEM was 120% after 100 h of equilibration
with DMMP vapours.
˚
on 4 A linde molecular sieve followed by distillation under
vacuum.
4.1. 2,2-Bis(4-allyoxyphenyl)hexafluoropropane (II)
Disodium salt of 4,40-(hexafluoroisopropylidene)diphenol
(7.6 g, 0.02 mol) in 50 ml of dry DMF was placed in a
250 ml three-necked round bottom flask, containing a
stirring bar and a dry nitrogen inlet, at room temperature.
Allyl bromide (7.26 g, 0.06 mol) was then added slowly
through a dropping funnel to the well-stirred mixture, which
immediately turned homogeneous. The reaction mixture was
further stirred for 30 min at room temperature. The course of
the reaction was followed by withdrawing a small aliquot
of the reaction mixture and then subjecting it to GC/MS
analysis. The reaction mixture was then filtered under
suction and the bulk of the DMF was removed by distillation
under vacuum. The yellow residue was then treated with
excess water in order to remove inorganic salt and remaining
DMF followed by extraction with dichloromethane. The
CH2Cl2 layer was dried and then removed by distillation.
The residue, a yellow viscous oil was then dried in a vacuum
oven at 50 8C to yield 2,2-bis(4-allyoxyphenyl)hexafluor-
opropane (7.41 g, 89%). The EI–MS data has been given in
Table 1; the 1H NMR data were consistent with the literature
report [4].
3. Conclusion
Fluorinated alcohols have been used as target structural
units in order to design new selective H-bond acidic
materials for piezoelectric studies. Nucleophilic displace-
ment reaction of allyl bromide with isolated disodium
salt of 4,40-(hexafluoroisopropylidene)diphenol in the
solvent DMF is a highly facile reaction. The product
when subjected to Claisen rearrangement yields 2,2-bis(3-
allyl-4-hydroxyphenyl)hexafluoropropane as candidate