For example, we synthesized a series of well-defined poly(norbornene)-based side
chain liquid crystalline brush block copolymers (LCBBCs) bearing cholesteryl mesogens in the first block and semicrystalline PEG (M n = 2000 g/mol) in the second block
(Deshmukh et al. 2013a). Morphologies of LCBBCs are investigated by scattering, and
microscopic techniques reveal various hierarchical structures as a result of the interplay
between the microphase segregation in brushlike macromolecules and the LC order.
We demonstrated the role of microphase segregation from brushlike PEG domains on
LC mesophase behavior. The synthesis of LCBBCs and their structure-property
relationship study can provide a useful template for the creation of stimuli-responsive
polymers (Li and Keller 2006; Lee et al. 2010). Effect of semicrystalline PEG on
complex hierarchical self-assembly is also further investigated through statistically
random LC brushlike copolymer (LCRBC) systems containing semicrystalline
brushlike PEG side chains and LC side chain (cholesterol or cyanobiphenyl)
containing comonomer (Deshmukh et al. 2013b; Mahajan et al. 2017). In case of
statistically random architectures, crystallinity of PEO domains is dependent on the
overall LC comonomer content. Higher content of side chain LC containing comonomer (>85 wt%) in LCRBCs results into amorphous (crystallization temperature, T c ~
À30 to À50
C) randomly embedded sphere-like PEO domains.
In current work, we prepare LCBBCs containing electrical and magnetic responsive cyanobiphenyl derivative as the LC block and PEG as the brushlike block unit
of composition wherein the PEG forms cylindrical domains within LC matrix. We
compare topology and structure of these materials to the structure formed by its
known linear counterparts. These materials will be useful for various stimuliresponsive applications including electrochemical devices and batteries.
Experimental Section
Synthesis
The monomers were synthesized as previously reported (Deshmukh et al. 2013a,
2014). A representative ring-opening metathesis polymerization (ROMP) of
LCBBC73 is described as below (Fig. 1). In separate vials NBCB 12 (0.8 g,
1.6 mmol) and NBMPEG (0.299 g, 0.14 mmol) with mG2nd (0.0315 mg,
0.043 mmol) are weighed. The vials are purged with nitrogen for 10 min after
which anhydrous CH 2 Cl 2 is added to each vial and stock solutions are prepared.
Then, catalyst solution in CH 2 Cl 2 is transferred to stirring NBCB 12 monomer
solution under inert atmosphere. After 15 min of polymerization of NBCB 12 ,
NBMPEG monomer solution is added under inert atmosphere. Polymerization of
second block is allowed for another 15 min at room temperature and terminated by
adding excess ethyl vinyl ether (EVE). The resulting polymer is precipitated in
methanol and then filtered, followed by drying overnight under vacuum at room
temperature.
482
L. Mahajan et al.
chain liquid crystalline brush block copolymers (LCBBCs) bearing cholesteryl mesogens in the first block and semicrystalline PEG (M n = 2000 g/mol) in the second block
(Deshmukh et al. 2013a). Morphologies of LCBBCs are investigated by scattering, and
microscopic techniques reveal various hierarchical structures as a result of the interplay
between the microphase segregation in brushlike macromolecules and the LC order.
We demonstrated the role of microphase segregation from brushlike PEG domains on
LC mesophase behavior. The synthesis of LCBBCs and their structure-property
relationship study can provide a useful template for the creation of stimuli-responsive
polymers (Li and Keller 2006; Lee et al. 2010). Effect of semicrystalline PEG on
complex hierarchical self-assembly is also further investigated through statistically
random LC brushlike copolymer (LCRBC) systems containing semicrystalline
brushlike PEG side chains and LC side chain (cholesterol or cyanobiphenyl)
containing comonomer (Deshmukh et al. 2013b; Mahajan et al. 2017). In case of
statistically random architectures, crystallinity of PEO domains is dependent on the
overall LC comonomer content. Higher content of side chain LC containing comonomer (>85 wt%) in LCRBCs results into amorphous (crystallization temperature, T c ~
À30 to À50
C) randomly embedded sphere-like PEO domains.
In current work, we prepare LCBBCs containing electrical and magnetic responsive cyanobiphenyl derivative as the LC block and PEG as the brushlike block unit
of composition wherein the PEG forms cylindrical domains within LC matrix. We
compare topology and structure of these materials to the structure formed by its
known linear counterparts. These materials will be useful for various stimuliresponsive applications including electrochemical devices and batteries.
Experimental Section
Synthesis
The monomers were synthesized as previously reported (Deshmukh et al. 2013a,
2014). A representative ring-opening metathesis polymerization (ROMP) of
LCBBC73 is described as below (Fig. 1). In separate vials NBCB 12 (0.8 g,
1.6 mmol) and NBMPEG (0.299 g, 0.14 mmol) with mG2nd (0.0315 mg,
0.043 mmol) are weighed. The vials are purged with nitrogen for 10 min after
which anhydrous CH 2 Cl 2 is added to each vial and stock solutions are prepared.
Then, catalyst solution in CH 2 Cl 2 is transferred to stirring NBCB 12 monomer
solution under inert atmosphere. After 15 min of polymerization of NBCB 12 ,
NBMPEG monomer solution is added under inert atmosphere. Polymerization of
second block is allowed for another 15 min at room temperature and terminated by
adding excess ethyl vinyl ether (EVE). The resulting polymer is precipitated in
methanol and then filtered, followed by drying overnight under vacuum at room
temperature.
482
L. Mahajan et al.