Phase Behavior of Polylactide-Based Liquid Crystalline Brushlike Block Copolymers

Abstract

We explore the morphology and phase behavior of a recently introduced architecture of liquid crystalline brushlike block copolymer (LCBBC) as functions of composition and molecular weight. Low-polydispersity materials were prepared by ring-opening metathesis polymerization of n-alkyloxy­cyano­biphenyl and poly­(dl-lactide) (PLA) functionalized norbornene monomers. Well-ordered block copolymer mesophases were observed with transitions from spheres to hexagonally packed cylinders, lamellae, inverse cylinders, and inverse spheres on increasing the weight fraction of the liquid crystalline block, f LC, from 0.15 to 0.85. The microdomain spacing displays a power-law scaling with molecular weight with an exponent of 0.6, L 0 ∼ MW0.6. The simple occurrence of microdomains with curved interfaces, spherical and cylindrical, and the sublinear scaling of microdomain spacing with molecular weight set this system clearly apart from bottlebrush block copolymers. We observe a peculiar morphology dependence of the liquid crystal anchoring condition with the cyanobiphenyl mesogens adopting planar anchoring at cylindrical microdomain interfaces while both homeotropic and planar anchoring were displayed at the block interface in lamellar systems.

Impact of intrinsic backbone chain stiffness on the morphologies of bottle-brush diblock copolymers

“…[2,9,12,14,15,21,24,36,40,41,43] However, the complete morphology map as a function of the BB molecular parameters is still under investigation. [6,9,10,12,16,32] In the classic phase diagram of linear diblock copolymers, the equilibrium morphology is determined by the balance between the competing block interfacial tension and the entropic penalty of stretching the polymer coils to fill the space uniformly. [1] Introducing an asymmetry in the segmental size/stiffness between the blocks, towards rod-coil copolymers, results in significant shifts of the boundaries between morphologies [19,39] at the cost of slowing down the self-assembly kinetics.…”

Grubbs’ and Schrock’s Catalysts, Ring Opening Metathesis Polymerization and Molecular Brushes—Synthesis, Characterization, Properties and Applications

“…There are four commercial products available: (a) l -lactide, LLA, (CAS: 4511-42-6), (b) d -lactide, DLA, (CAS: 13076-17-0), (c) the racemic mixture of d - and l -lactide, DLLA, (CAS: 95-96-5) and meso -lactide (CAS: 13076-19-2). The majority of the studies on lactide bottlebrushes involve PDLLA side chains (23 articles) [ 36 , 49 , 58 , 99 , 111 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 , 142 , 143 , 144 ]. There are only 10 articles with PLLA side chains [ 12 , 34 , 44 , 50 , 56 , 57 , 104 , 108 , 116 , 145 , 146 , 147 , 148 ] and one article where PDLA (and PLLA) side chains are used [ 145 ].…”

“…Pseudo-alternating bottlebrushes with two different chains per monomeric unit ( Figure 4 D) are: PEO/PLLA [ 56 ], PS/PLLA [ 104 , 116 ], PS/PDLLA [ 58 , 99 ]. Molecular brushes with umbrella-like structure ( Figure 4 F) have been prepared with a variety of norbornene derivatives for specialized purposes [ 108 , 132 , 133 , 134 , 135 , 140 , 141 , 144 ]. Core–shell structures ( Figure 4 E) have been synthesized with PLLA-b-PHIC diblock side chains [ 148 ].…”

“…These liquid crystalline materials have shown magnetic field directed self-assembly [ 132 , 133 ] and membranes with aligned pores have been prepared [ 141 ]. The morphology of the bottlebrushes has been studied and well-ordered mesophases were observed with transitions from spheres to hexagonally packed cylinders, lamellae, inverse cylinders, and inverse spheres depending on the weight fraction of the liquid crystalline block [ 134 ]. The authors were interested in generating aligned nanoporous materials using low-cost permanent magnets [ 140 ].…”

Cooperative and Independent Effect of Modular Functionalization on Mesomorphic Performances and Microphase Separation of Well‐Designed Liquid Crystalline Diblock Copolymers

“…However, few attempts have been made to reveal the independent and cooperative effect of different functions on LC properties and microphase separation of LCBCPs . The synthesis and complete characterization of LCBCPs with well‐designed functions in different blocks of BCPs, i.e., modular functionalization, are challenging but valuable to be explored …”