K. Zhang et al. / Polymer 51 (2010) 2809e2817
2811
eluent. The red product (1.6 g) was obtained in a yield of 60%. 1H NMR
(CDCl3) (ppm): 7.91-7.89 (2H, d), 7.58-7.54 (1H, t), 7.41-7.37 (2H, d),
4.72(2H, s), 2.72-2.59 (4H, m), 1.95 (3H, s).
composition was determined by 1HNMR spectrum. Mn
d
¼ 79600, Mn SEC ¼ 148900, Mw/Mn ¼ 1.15.
NMR
2.7. Bulk casting and annealing of P2VP-b-PTEPM-b-PS
2.3. Synthesis of PTEPM macromolecular chain transfer agent
(Macro-CTA)
A solution of P2VP-b-PTEPM-b-PS triblock copolymer (50 mg/
mL) in THF, CHCl3 or benzene was spread onto a clean Teflon plate
and the solvent was allowed to evaporate in a vacuum desiccator
over 5 days. The resulting bulk sample (ca. 0.5 mm in thickness)
was then dried for 12 h under vacuum at 60 ꢀC.
Bulk reversible addition-fragmentation chain transfer (RAFT)
polymerization of TEPM was performed in a sealed ampule
equipped with a stir bar under vacuum. The procedure was as
follows: CTA1 (116.0 mg, 3.65 ꢁ10ꢂ1 mmol), TEPM (11.67 g,
40.2 mmol) and AIBN (6.0 mg, 3.65 ꢁ10ꢂ2 mmol) were added into
a 50 mL glass ampule. The mixture was degassed through four
freeze-evacuate-thaw cycles and then the ampule was sealed under
vacuum. Polymerization was carried out in an oil bath at 60 ꢀC for
18 h and was terminated by cooling with an ice bath. The resulted
crude product was purified by precipitating into a large amount of
methanol and water mixture (7:3 volume ratio) three times.
Monomer conversion was determined by 1H NMR spectrum. Mn
2.8. Self-assembly of P2VP-b-PTEPM-b-PS with stearic acid
A solution of P2VP-b-PTEPM-b-PS triblock copolymer (50 mg/
mL, 2 mL) and stearic acid (0.36 mg) in CHCl3, where the molar ratio
between 2VP unit and stearic acid was fixed to 1:1, was spread onto
a clean Teflon plate and the solvent was allowed to evaporate in a
vacuum desiccatorover5 days. The resultingbulk sample (ca. 0.5 mm
in thickness) was then dried for 12 h under vacuum at 60 ꢀC.
¼ 17300, Mn SEC ¼ 13700, Mw/Mn ¼ 1.15.
NMR
2.9. Gelation in microdomain structure and preparation of
nanoobjects
2.4. Synthesis of PTEPM-b-PS diblock copolymer
The polymerization was performed in a sealed ampule equipped
Bulk samples with microphase separation structure were
exposed to HCl atmosphere for about 8 h and then dried under
vacuum at temperature of 60 ꢀC for 12 h to carry out the sol-gel
reaction of the PTEPM domain completely. The nanoobjects were
prepared by dispersing the gelated bulk samples in THF or CHCl3
three days.
with
a stir bar under vacuum. PTEPM macro-CTA (3.18 g,
1.84 ꢁ10ꢂ1 mmol) and styrene (57.50 g, 552.1 mmol) were charged
into a 150 mL Schlenk flask. The mixture was degassed by four
freeze-evacuate-thaw cycles and then flame-sealed under vacuum.
Polymerization was carried out in an oil bath thermostated at 90 ꢀC
for 12 h. The reaction was terminated by cooling of the solution to
room temperature and the mixture was exposed to air. The
resulting product dispersed in THF was purified by precipitating
into methanol three times. The composition was determined by 1H
NMR spectrum. Mn NMR ¼ 50800, Mn SEC ¼ 49700, Mw/Mn ¼ 1.15.
2.10. Supporting gold nanoparticles into nanofibers
After dispersing gelated hybrid bulk materials (5 mg) from THF
annealing solvent in THF (2 mL) and stirred three days, a water
solution of NaAuCl4 (ca. 1 mg/mL) was added slowly, where the
molar ratio between 2VP and NaAuCl4 was fixed to 1:0.2. When the
mixture solution was stirred ca. 24 h, a freshly prepared aqueous
solution of sodium borohydride (10 mg/mL) (ca. 0.1 mL) was added
dropwise under vigorously stirring. After the addition was finished,
the stirring was kept about 10 h.
2.5. Synthesis of P2VP homopolymer
The polymerization was also performed in a sealed ampule
equipped with
a stir bar under vacuum. CTA2 (66.80 g,
1.83 ꢁ 10ꢂ1 mmol), 2-vinylpyridine (13.70 g, 290.1 mmol) and AIBN
(12.8 mg, 77.9 mmol) were charged into a 50 mL Schlenk flask. The
mixture was degassed by four freeze-evacuate-thaw cycles and
then flame-sealed under vacuum. Polymerization was carried out
in an oil bath thermostated at 60 ꢀC for 9 h. The crude product
dispersed in THF was purified by precipitating into hexane three
times. The block ratio was determined by 1H NMR spectrum. Mn
2.11. Loading 1-bromohexane into nanofibers by quaternization
To load 1-bromohexane into the core of nanofibers from THF
annealing solvent by quaternization, the dispersed nanofibers were
collected from THF by centrifugation and then put into 1-bromo-
hexane (1 mL). The reaction mixture was sealed and stirred for 48 h
at 70 ꢀC. At last, the quaternized nanofibers were thoroughly rinsed
by THF no less than 5 times to remove the unreacted 1-bromo-
hexane completely, and then dispersed in chloroform.
¼ 33900, Mn SEC ¼ 102500, Mw/Mn ¼ 1.15.
NMR
2.6. Synthesis of P2VP-b-PTEPM-b-PS triblock copolymer
The PTEPM-b-PS-b-P2VP triblock copolymer was synthesized by
click chemistry from PTEPM-b-PS diblock copolymer and P2VP
homopolymer. PTEPM-b-PS diblock copolymer (1.93 g, Mn
2.12. Loading 1-capric acid into nanofibers by hydrogen-bonding
¼ 33900, Mw/Mn ¼ 1.09), P2VP (6.26 g, Mn
¼ 50800, Mw/
To load 1-capric acid into the core of nanofibers from THF
annealing solvent by hydrogen-bonding, the dispersed hybrid
nanofibers with deprotonated P2VP microdomain (5 mg) and
1-capric acid were mixed together in chloroform (2 mL), where the
molar ration between the 1-capric acid and pyridine group was
about 1.1:1. After the mixtures were stirred for 12 h, the chloroform
was slowly removed by evaporation at room temperature.
Conv.
Mn ¼ 1.15),
NMR
tris[2-(dimethylamino)ethyl]amine
(127.2 mg,
5.53 ꢁ10ꢂ1 mmol) and DMF (30 mL) were charged into a 100 mL
Schlenk flask. The mixture was degassed by four freeze-evacuate-
thaw cycles and then CuBr (79.3 mg, 5.53 ꢁ 10ꢂ1 mmol) was added
under the protection of N2. After evacuating another 10 min, the
flask was sealed under vacuum. The click chemistry was carried out
at room temperature for 10 h. The crude product was diluted by
THF and passed a basic alumina column to remove the catalyst. The
polymer was firstly precipitated in hexane, methanol and finally
ethyl ether to remove excessive P2VP. The overall yield of purified
PTEPM-b-PS-b-P2VP triblock copolymer was ca. 50%. The
2.13. Characterization
Gel permeation chromatography (GPC) was performed by a set
of a Waters 515 HPLC pump, a Waters 2414 refractive index