in conventional liquid crystals, have remarkable mechanical properties which can be
the starting point of the analogy between LCs and biomaterials (Belamie et al. 2006).
Advantages of liquid crystallinity in biological material processing have been
reported in the past (Neville 1993; Fratzl 2003; Ikoma et al. 2003; Fratzl and GiraudGuille 2011; Rey 2010) and can be summarized as follows:
(i) Efficient packing in DNA solutions and virus solutions
(ii) Surface directed self-assembly in cellulose fibers to create plant-based biological plywoods
(iii) Low viscosity for flow processing observed in silk spinning
(iv) Sensor/actuator abilities observed in plants and membranes
(v) Mechanical strength: Plant cell walls exo-cuticle of insects made of chitin and
collagen fibrils in human compact bones
Table 1 shows a partial compilation of biological mesogens that exhibit mesophases in forms of tissues, cells, and supramolecular self-assembled materials. The
observed mesophases of BLCs can be classified into: (i) solid biological analogues
(left column) denominated as plywoods in the literature (Rey 2010), where structural
building blocks display liquid crystalline arrangements in a frozen state but a selfassembly process is required for its morphogenesis (Giraud-Guille 2005; Belamie
et al. 2006), (ii) liquid crystalline phases observed in biopolymer solutions in a
controlled environment (middle column), and (iii) mesophases observed in its native
state (right column). Mesophase order is ubiquitous in the development of functional
and structural biological materials (Rey 2007, 2009, 2010). The mesophase ordering
and topological defects in biological analogues is usually that of chiral nematics
(cholesteric) and hence they are referred as biological helicoidal plywoods (Rey
2007, 2009, 2010; Murugesan et al. 2011; Rey et al. 2014). Hence these biological
liquid crystalline materials have attracted immense research interest. Periodic undulations resulting from interactions between chirality and interface capillarity in
cholesteric collagen solutions under shear and in film casting processes have not
been fully understood yet.
The process conditions differ drastically between synthetic and biological liquid
crystals while synthetic materials such as polyamides (Kevlar) require strong solvents to form nematic phases whereas natural biological polymers that are usually
semiflexible and charged carbohydrates, proteins, and DNA self-assemble under
ambient conditions (Rey 2007, 2009, 2010; Rey and Herrera-Valencia 2012).
The advantages of water-based processing and biological compatibility of silk
fibers, while displaying excellent mechanical properties, are behind the continuing
interest in this area (Rey and Herrera-Valencia 2012; Rey 2007, 2009, 2010). Some
important geometries that have been explored due to its possible applications include
thin films (nematic foams and shells, plant cell walls) and in quasi 1D geometries
such as contact lines in evaporating drops and filaments potentially applicable for
functional applications, including sensor/actuator, displays, lubrication, detergency,
catalysis, rheological modifiers, and coatings, among others (Rey 2007, 2008a, b,
2009; Rey and Herrera-Valencia 2012).
10 Liquid Crystalline Polymers: Structure and Dynamics
279
the starting point of the analogy between LCs and biomaterials (Belamie et al. 2006).
Advantages of liquid crystallinity in biological material processing have been
reported in the past (Neville 1993; Fratzl 2003; Ikoma et al. 2003; Fratzl and GiraudGuille 2011; Rey 2010) and can be summarized as follows:
(i) Efficient packing in DNA solutions and virus solutions
(ii) Surface directed self-assembly in cellulose fibers to create plant-based biological plywoods
(iii) Low viscosity for flow processing observed in silk spinning
(iv) Sensor/actuator abilities observed in plants and membranes
(v) Mechanical strength: Plant cell walls exo-cuticle of insects made of chitin and
collagen fibrils in human compact bones
Table 1 shows a partial compilation of biological mesogens that exhibit mesophases in forms of tissues, cells, and supramolecular self-assembled materials. The
observed mesophases of BLCs can be classified into: (i) solid biological analogues
(left column) denominated as plywoods in the literature (Rey 2010), where structural
building blocks display liquid crystalline arrangements in a frozen state but a selfassembly process is required for its morphogenesis (Giraud-Guille 2005; Belamie
et al. 2006), (ii) liquid crystalline phases observed in biopolymer solutions in a
controlled environment (middle column), and (iii) mesophases observed in its native
state (right column). Mesophase order is ubiquitous in the development of functional
and structural biological materials (Rey 2007, 2009, 2010). The mesophase ordering
and topological defects in biological analogues is usually that of chiral nematics
(cholesteric) and hence they are referred as biological helicoidal plywoods (Rey
2007, 2009, 2010; Murugesan et al. 2011; Rey et al. 2014). Hence these biological
liquid crystalline materials have attracted immense research interest. Periodic undulations resulting from interactions between chirality and interface capillarity in
cholesteric collagen solutions under shear and in film casting processes have not
been fully understood yet.
The process conditions differ drastically between synthetic and biological liquid
crystals while synthetic materials such as polyamides (Kevlar) require strong solvents to form nematic phases whereas natural biological polymers that are usually
semiflexible and charged carbohydrates, proteins, and DNA self-assemble under
ambient conditions (Rey 2007, 2009, 2010; Rey and Herrera-Valencia 2012).
The advantages of water-based processing and biological compatibility of silk
fibers, while displaying excellent mechanical properties, are behind the continuing
interest in this area (Rey and Herrera-Valencia 2012; Rey 2007, 2009, 2010). Some
important geometries that have been explored due to its possible applications include
thin films (nematic foams and shells, plant cell walls) and in quasi 1D geometries
such as contact lines in evaporating drops and filaments potentially applicable for
functional applications, including sensor/actuator, displays, lubrication, detergency,
catalysis, rheological modifiers, and coatings, among others (Rey 2007, 2008a, b,
2009; Rey and Herrera-Valencia 2012).
10 Liquid Crystalline Polymers: Structure and Dynamics
279