Paper
RSC Advances
SMPU30. In SMPU30, the PCL segments act as the switching
domain and the PU segments with carboxyl groups are as the
fixing domain. Based on the dual shape memory effect of
SMPU30, we anticipate that the triple-shape memory property
can be generated by the formation of the new mesogen
pendant PU segments as a second fixing domain via adding
INChs into the PU segments attached by the H-bonding
interactions.
IR (KBr): n = 2952(s), 2892(s), 2867(s), 1724 (vs.; vs.(CLO)), 1560,
2
1
1469 (m; aromatic CLC), 1281(s; vas(C–O–C)), 1123 cm (s;
1
vs.(C–O–C)). H NMR (CDCl3): d = 8.78 (s, 2H, ArH), 7.88 (s, 2H,
ArH), 5.43 (m, 1H, CHLC), 4.88 (m, 1H, C(O)OCHCH
H, C(O)OCHCH ), 2.01–0.69 (41H, CH, CH , CH ).
Synthesis of SMPU30-INCh-n. SMPU30 and INCh were
2
), 2.48 (m,
2
2
2
3
dissolved in appropriate amount of DMF and CHCl respec-
3
tively. The two solutions were mixed and stirred for 1 h at 70
uC. Then the solution was poured out and evaporated to
remove the DMF at 80 uC for 8 h to form a film. To remove the
organic solvent completely, the film was dried under vacuum
at room temperature for 48 h.
Experimental
Materials
Characterizations
2
e-Caprolactone (CL), Stannous octoate [Sn(Oct) , 95%] were
The structure of INCh and molecular weights of the PCL diols
were determined by H NMR (Bruker Unity-400, Mn). FT-IR
purchased from Aldrich. CL was purified by drying over CaH2
and distilled under reduced pressure. 4,4-Diphenylmethane
diisocyanate (MDI), was purchased from Tokyo Chemical
industry Co. LTD. 2,2-Bis(hydroxymethyl) propionic acid
1
spectroscopic analysis was carried out with a Nicolet 5700 FTIR
spectroscope (Thermo Electron, USA). Each sample for
infrared analysis was prepared by scraping powder to press a
pellet with KBr. Samples were heated from 20 uC to 180 uC.
After reaching each desired temperature and isothermy for 1
min to record, the infrared spectra were recorded between
(DMPA, 99%) was purchased from Acros Organics, USA.
Ethylene glycol (EG), pentaerythritol (PER), N,N-dimethyl
formamide (DMF), isonicotinic acid, cholesterol were pur-
chased from Kelong chemical reagent factory in Chengdu. EG
was distilled under a reduced pressure. DMF was dried over
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21 1
4
000 and 400 cm with the resolution of 4 cm . H solid-
state NMR experiments were performed on a Bruker Avance III
spectrometer with frequencies of 400 kHz, Hahnecho MAS
measurements, a 1.3 mm MAS probe and spinning of 60 kHz.
Thermal analysis was conducted by using a differential
scanning calorimeter (DSC-Q100, TA, USA) at heating and
CaH for 2 days at room temperature, distilled under vacuum,
2
and stored in the presence of 4 Å molecular sieves. Unless
otherwise noted, all chemical reagents were obtained from
commercial suppliers and used without further purification.
Preparation of PCL diols (HO–PCL–OH). CL (360 mmol), EG
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cooling rates of 10 uC min . All runs were carried out with
2
(10 mmol) and Sn(Oct) (0.1 mmol) were added into a single
samples of ca. 2–5 mg. Static tensile test was accomplished at
neck flask with stirring and vacuum for 4 h at room
temperature. Then the flask was put into an oven for reacting
for 6 h at 150 uC. After cooling, the polymer was dissolved in a
small amount of CHCl3 and was precipitated into cold
methanol. Finally the polymer was dried in vacuum for 48 h.
Molecular weight of PCL diols is about 4100 Da measured by
2
1
the cross-head speed of 2 mm min at room temperature
using a universal testing machine Instron 5567 (Instron Co.,
Massachusetts). Dynamic mechanical properties were deter-
mined with a dynamic mechanical thermal analyzer (DMA-
Q800, TA, USA), in the tensile resonant mode, at a heating rate
2
1
1
of 3 uC min and 1 Hz.
H NMR.
Synthesis of SMPU30. PCL diols (4 mmol), MDI (8 mmol),
2
Sn(Oct) (0.02 mmol) and 50 mL of DMF were charged into a
dried flask and reacted for about 1 h at 80 uC. Then, DMPA (30
mmol) and MDI (30 mmol) were successively added, with the
reaction being maintained at the same temperature for 2 h,
after that pentaerythritol (2 mmol) was added. Reacted at the
same temperature for another 1 h, the solution was poured out
and evaporated at 80 uC for 8 h; then obtained films were
further dried under vacuum at room temperature for another
Results and discussion
The confirmation of hydrogen bonded interaction
H-bonding interactions between the NH groups and CLO
groups in single polyurethane polymer have been studied.
3
2–34
In general, the mechanism of H-bonding interaction is very
complex, especially for polymers. In SMPU30, there are several
kinds of H-bonding pairs, such as H-bonding interaction
between COOH dimer, COOH and CLO (CLO in urethane and
PCL), NH and CLO (CLO in urethane, PCL and COOH). After
introducing INCh, both the electron-rich pyridine ring and
ester group of INCh compete with the original CLO of SMPU30
to form new H-bonding pairs. To confirm it, we selected
polyethyleneimine (PEI) without CLO and with NH to replace
SMPU30 to investigate whether there exists H-bonding inter-
actions between PEI and INCh. From the FT-IR spectrum in
4
8 h.
Synthesis of INCh. Isonicotinic acid (16 mmol) and SOCl2
20 mmol) react at 70 uC for 4 h, then distilled the excessive
SOCl under reduced pressure. Later, 16 mmol of cholesterol
in 40 mL of CH Cl containing 1 mL of pyridine was dropped
(
2
2
2
in the reaction bottle soaked in ice bath for 0.5 h. After stirring
at room temperature for 1 h, the solution was refluxed for
another 8 h. After it was finished and cooled to room
temperature, the reaction solution was washed by distilled
water two times and collected the organic solution. After
removing the solvent, the solid was purified by column
chromatography and recrystallized from ethanol, dried under
vacuum for 24 h. Finally the INCh white powder was acquired.
3
Fig. S1, ESI , it can be clearly seen that there are no H-bonding
interactions between CLO in ester group of INCh and NH of
PEI because the CLO stretching does not change. In addition,
no H-bonding interaction can be found between pyridine ring
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050 | RSC Adv., 2013, 3, 7048–7056
This journal is ß The Royal Society of Chemistry 2013