Figure 6.2
 
117
Nematic Ordered Cellulose Templates
Another.important.feature.of.the.OH.groups.is.the.type.of.hydroxymethyl.
conformation.at.the.C6.position,.because.the.conformation.of.C5–C6.and.the.
resulting.interactions.including.inter-.and.intramolecular.hydrogen.bonds.
in.the.cellulose.structure.may.differ.from.that.in.crystallites,.and.also.it.is.
assumed.to.make.up.the.extent.of.crystallization,.as.well.as.the.final.morphology.of.cellulose..In.the.noncrystalline.regions,.the.rotational.position.of.
nate.or.totally.nonoriented,.which.are.not.identical.with.those.in.the.crystallites..Therefore.it.was.important.to.confirm.the.type.of.O6.rotational.position.
with.respect.to.the.O5.and.C4.in.a.β-glucan.chain.by.employing.CP/MAS.
13 C. NMR. (Horii. et. al.. 1983).. The. type. of. hydroxymethyl. conformations. is.
gauche-trans.(gt),.trans-gauche.(tg),.or.gauche-gauche.(gg).at.the.C6.position.
in.carbohydrates..As.for.the.noncrystalline.states,.they.are.considered.to.be.
the.gg.conformation.(see.Figure 6.2).
NOC. is. prepared. by. uniaxial. stretching. of. water-swollen. cellulose. from.
the.N,N-dimethylacetamide.(DMAc)/LiCl.solution.at.a.draw.ratio.of.2.0.to.
provide. highly. oriented. β-1,4-glucan. molecular. chains. of. cellulose. toward.
the.stretching.axis.(Togawa.and.Kondo.1999)..When.the.dissolved.cellulose.
molecules.in.the.DMAc/LiCl.system.are.self-aggregated.in.water.vapor.to.
form.a.gel,.presumably.with.a.minimum.amount.of.restricted.engagements.
among.the.hydrophobic.sites.of.the.ring.previously.described,.it.is.stretched.
O(1')
OH
C(5)
C(4)
C(1)
OH
H(6)"
H(6')
O(1')
H(6)
OH(6)
C(1) O(1')
H(6)"
OH(6)"
1"
3"
4"
OH
O(5)
O
O
O
O
H
OH(6)
gg
gg
H(6)
H(6)
C(5)
C(4)
O(5)
OH(6)
H(6')
H(6)
C(1)
C(5)
C(4)
O(5)
O(1')
H(6)
OH(6)
H(6')
C(1)
C(5)
C(4)
O(5)
5" 2"
H(5)
H(5)
H(5)
gt
gg
tg
Figure 6.2
Schematic.diagram.of.the.hydroxymethyl.conformations.at.the.C6.position,.that.is,.the.orientation.of.the.C6–O6.bond,.gauche-trans.(gt),.trans-gauche.(tg),.or.gauche-gauche.(gg).with.a.
cellobiose.unit.