Thermal Analysis
TA-2920 DSC (Q-100 series) instrument is used to analyze thermal properties of the
copolymer. Indium standard is used to calibrate instrument. Roughly 5–10 mg of
polymer sample is taken, and scanning rate of 10
C/min is used. Phase transition
temperatures are determined by the first cooling or the second heating cycle using
TA universal analysis software.
Thermal gravimetric analysis (TGA) was performed on PerkinElmer TGA
Q-500. The sample (6–10 mg) was heated from room temperature to 600
C at a
ramping rate of 20
C/min under nitrogen flow. The TA universal analysis software
was used to obtain the degradation temperature of the polymer.
Small-Angle X-Ray Scattering (SAXS) (Performed at University
of Connecticut)
SAXS is performed on a pin-hole collimated Rigaku SMAX3000 instrument configured with CuKα radiation (1.542 Å) produced by a micro-focus source. The beam
diameter on the sample plane is 1 mm and the scattered intensity is recorded on a
gas-wire electronic area (2D) detector. The area detector has a resolution of 1024 Â
1024 pixels and is located at a distance of ~ 150 cm from the sample. The instrument
is calibrated using Silver behenate standard with a d-spacing of 58.38 Å. SAXS data
acquired is plotted as intensity (I) versus scattering vector q, where q = (4π/λ) Â sin θ,
(2θ is the scattering angle).
Results and Discussions
Synthesis
Two monomers, norbornenyl end functionalized PEG, where M n of PEG
chains = 2000 g/mol (NBMPEG) (Deshmukh et al. 2013) and cyanobiphenyl liquid
crystalline units attached with 12 methylene spacer to norbornene (NBCB 12 )
(Deshmukh et al. 2014), are synthesized according to previously reported procedures. Representative LCBBCs are synthesized by sequential ring-opening metathesis polymerization (ROMP) using a modified Grubbs catalyst second generation
(mG2nd) ((H 2 IMes)-(pyr) 2 (Cl) 2 RuCHPh) (Love et al. 2002) using monomers
NBMPEG and NBCB 12 (Fig. 2). The compositions of LCBBCs are determined by
integrating characteristic peaks of NBCB12 (a proton at 6.9 ppm) and NBMPEG
(three protons at 3.36 ppm) in
1 H NMR spectra and by comparing the ratio of their
integration values (Fig. 2). The number average of molecular weight and polydispersity index of LCBBCs was determined using gel permeation chromatography
(GPC) using THF as the eluent at room temperature. We will use the following
17 New Stimuli-Response Liquid Crystalline Polymer Architectures
483
TA-2920 DSC (Q-100 series) instrument is used to analyze thermal properties of the
copolymer. Indium standard is used to calibrate instrument. Roughly 5–10 mg of
polymer sample is taken, and scanning rate of 10
C/min is used. Phase transition
temperatures are determined by the first cooling or the second heating cycle using
TA universal analysis software.
Thermal gravimetric analysis (TGA) was performed on PerkinElmer TGA
Q-500. The sample (6–10 mg) was heated from room temperature to 600
C at a
ramping rate of 20
C/min under nitrogen flow. The TA universal analysis software
was used to obtain the degradation temperature of the polymer.
Small-Angle X-Ray Scattering (SAXS) (Performed at University
of Connecticut)
SAXS is performed on a pin-hole collimated Rigaku SMAX3000 instrument configured with CuKα radiation (1.542 Å) produced by a micro-focus source. The beam
diameter on the sample plane is 1 mm and the scattered intensity is recorded on a
gas-wire electronic area (2D) detector. The area detector has a resolution of 1024 Â
1024 pixels and is located at a distance of ~ 150 cm from the sample. The instrument
is calibrated using Silver behenate standard with a d-spacing of 58.38 Å. SAXS data
acquired is plotted as intensity (I) versus scattering vector q, where q = (4π/λ) Â sin θ,
(2θ is the scattering angle).
Results and Discussions
Synthesis
Two monomers, norbornenyl end functionalized PEG, where M n of PEG
chains = 2000 g/mol (NBMPEG) (Deshmukh et al. 2013) and cyanobiphenyl liquid
crystalline units attached with 12 methylene spacer to norbornene (NBCB 12 )
(Deshmukh et al. 2014), are synthesized according to previously reported procedures. Representative LCBBCs are synthesized by sequential ring-opening metathesis polymerization (ROMP) using a modified Grubbs catalyst second generation
(mG2nd) ((H 2 IMes)-(pyr) 2 (Cl) 2 RuCHPh) (Love et al. 2002) using monomers
NBMPEG and NBCB 12 (Fig. 2). The compositions of LCBBCs are determined by
integrating characteristic peaks of NBCB12 (a proton at 6.9 ppm) and NBMPEG
(three protons at 3.36 ppm) in
1 H NMR spectra and by comparing the ratio of their
integration values (Fig. 2). The number average of molecular weight and polydispersity index of LCBBCs was determined using gel permeation chromatography
(GPC) using THF as the eluent at room temperature. We will use the following
17 New Stimuli-Response Liquid Crystalline Polymer Architectures
483