Evaluation Only. Created with Aspose.PDF. Copyright 2002-2021 Aspose Pty Ltd.
Macromolecules
Article
Scheme 1. Synthetic Route of TVP
pressure of the WEEE Directive and RoHS legislation.10,14,23 It
is noted that polyphosphonates exhibit good transparency and
melt-processability, whereas their low n values (below 1.65)
and poor hydrolytic stability during long-term use restrict their
application.21 Therefore, developing halogen-free phospho-
rous-containing transparent polymers with high n values (n >
1.7) are of great significance for applications. To elevate the n
values of phosphorous-containing polymers, highly polarizable
sulfur atoms have been incorporated into the polymers through
a thiol-ene “click” reaction.24−26 Nevertheless, these phos-
phorous- and sulfur-containing polymers exhibit unsatisfying n
and thermostability due to the existence of the carbonyl groups
with low molar refraction and the flexible alkyl thioether
linkages resulting in low thermostability. Thus, developing new
phosphorus-containing HRIPs with desirable thermal and
mechanical properties still remains a challenge.
To address this issue, we have designed a new halogen-free
phosphorus-containing monomer (TVP), based on which the
phosphorus-containing HRIPs can be effectively prepared via a
thiol-ene click reaction with a bifunctional aromatic thiol
(TDTH). Highly polarizable phosphorus, sulfur atoms, and
aromatic groups have been incorporated into the polymers
through a facile and reliable thiol-ene click reaction to improve
the n values and thermostability of the polymer. To obtain the
monomer by a facile method, TVP is designed to be prepared
from a bio-based aldehyde (4-hydroxybenzaldehyde) as the
raw material.27−29 Preparing polymers from natural biomass
resources has recently attracted growing interest in academia
or industry. This is because besides their easy availability, they
are prone to obtain new polymers with particular properties,
which cannot be facilely obtained from traditional chem-
icals.30−32 Commercial 4,4′-thiodibenzenethiol (TDTH) in-
stead of alkyl thioether was chosen as the thioaryl ether
monomer due to its rigid structure making for the thermal
stability of the polymers. Phosphorous-sulfide polymers
exhibited high transmittance, high n values, and good
thermostability. In this paper, we not only provide a new
strategy to prepare phosphorus-containing HRIPs with good
thermal stability but also expand the access of starting materials
for HRIPs. Herein, we report the detailed results.
recorded on an Agilent 5973 N detector with ionization mode of
electrospray ionization (ESI). Elemental analysis (EA) was measured
at room temperature on an Elementar VARIO ELIII apparatus. The
thickness of free-standing films was measured by a numerical
micrometer gauge. Thermogravimetric analysis (TGA) was performed
on a Netzsch TG 209F1 TGA tester from 35 to 1000 °C in N2 at a
heating rate of 10 °C min−1. UV−vis−near-infrared (NIR) spectra
were detected on a Varian CARY 5000 detector in the wavelength
range from 300 to 2500 nm. Differential scanning calorimetry (DSC)
analysis was measured on a TA Instrument DSC Q200 from 40 to
180 °C at a heating rate of 10 °C min−1 in N2. Atomic force
microscopy (AFM) was utilized for measuring the surface toughness
of the polymer films with an area of 2 μm × 2 μm. Contact angles of
the polymer films were defined on JC2000 C. Dynamic mechanical
analysis (DMA) was measured on DMA 8000 from 40 to 180 °C at a
heating rate of 5 °C min−1 at 1 Hz in air. X-ray diffraction (XRD) was
obtained on a PANalytical X’Pert Pro MPD instrument. n and the
extinction coefficient (κ) of the films were obtained by using an
ellipsometer at an angle of incidence of 65° from 350 to 900 nm
wavelength range.
Synthesis of 4-Vinylphenol. A mixture of methyltriphenylphos-
phonium bromide (25.01 g, 70.0 mmol), potassium tert-butoxide
(15.71 g, 140.0 mmol), and sodium hydride (1.40 g, 35.0 mmol) in
tetrahydrofuran (THF, 80 mL) was stirred for 10 min at room
temperature. Then, a solution of 4-hydroxybenzaldehyde (8.55 g, 70.0
mmol) in THF (40 mL) was added dropwise for about 1 h. After
stirring for 18 h, the system was neutralized with diluted HCl and
extracted with ethyl acetate. The organic phase was washed with
saturated saline and dried over anhydrous Na2SO4. The solvent was
removed by a rotary evaporator, and the obtained residue was purified
by column chromatography to obtain a white solid in a yield of 95%.
1H NMR (CDCl3, 400 MHz), δ (ppm): 7.31 (d, J = 8.3 Hz, 2H), 6.80
(d, J = 8.3 Hz, 2H), 6.65 (dd, J = 17.5, 10.9 Hz, 1H), 5.60 (d, J = 17.6
Hz, 1H), 5.21 (s, 1H), 5.12 (d, J = 10.9 Hz, 1H). 13C NMR (dimethyl
sulfoxide (DMSO)-d6, 100 MHz), δ (ppm): 157.2, 136.2, 128.1,
127.3, 115.2, 110.5. HRMS-ESI (m/z): calcd for C8H9O [M + H]+
121.0648; found, 121.0648.
Synthesis of TVP. A solution of phosphorus oxychloride (1.70 g,
11.1 mmol) in ethyl acetate (20 mL) was added dropwise to a
solution of 4-hydrostyrene (3.20 g, 27.0 mmol) and triethylamine
(3.37 g, 33.3 mmol) in ethyl acetate (50 mL) at −10 °C for about 0.5
h. After maintaining at −10 °C for 0.5 h, the reaction system was
stirred at room temperature for 10 h. After being filtered, extracted
with ethyl acetate, washed with saturated saline, and evaporated the
solvent, a residue was obtained. This residue was purified by column
1
chromatography to obtain a colorless liquid in a yield of 77%. H
EXPERIMENTAL SECTION
■
NMR (CDCl3, 400 MHz), δ (ppm): 7.39 (d, J = 8.6 Hz, 1H), 7.24−
7.14 (m, 1H), 6.68 (dd, J = 17.6, 10.9 Hz, 1H), 5.70 (d, J = 17.6 Hz,
1H), 5.25 (d, J = 10.9 Hz, 1H). 13C NMR (100 MHz, CDCl3) δ
(ppm): 149.9 (d, J = 5.0 Hz), 135.6 (s), 135.2 (s), 127.6 (s), 120.2 (d,
J = 5.0 Hz), 114.3 (s). 31P NMR (CDCl3, 121 MHz), δ (ppm):
−17.09. HRMS-ESI (m/z): calcd for C24H22O4P [M + H]+ 405.1250;
found, 405.1251. Anal. calcd for C24H21O4P: C: 71.28, H: 5.23, P:
7.66. Found: C: 71.30, H: 5.44, P: 7.55.
Formation of Free-Standing Films. TVP (108 mg, 0.27 mmol
or 160 mg, 0.40 mmol) was added dropwise to a stirring solution of
4,4′-thiodibenzenethiol (TDTH, 100 mg, 0.40 mmol) in chlor-
obenzene (1 mL) at room temperature. After stirring for 5 min, the
Materials and Measurements. 4-Hydroxybenzaldehyde and
4,4′-thiodibenzenethiol (TDTH) were purchased from TCI Com-
pany. Methyltriphenylphosphonium bromide, potassium tert-butox-
ide, and sodium hydride were purchased from MACKLIN Company.
Phosphorus oxychloride and trimethylamine were purchased from
Adamas Company, China. All solvents were utilized as received.
Fourier-transform infrared (FTIR) and attenuated total reflection
Fourier-transform infrared (ATR-FTIR) spectra were carried out on a
1
Nicolet spectrometer. H nuclear magnetic resonance (NMR), 13C
NMR, and 31P NMR spectra were measured on an Agilent 500/54/
ASP spectrometer. High-resolution mass spectra (HRMS) were
B
DOI: 10.1021/acs.macromol.9b01770
Macromolecules XXXX, XXX, XXX−XXX