Classification and Examples of Liquid Crystals - Revision history

Cmditradmin: /* Nematic Liquid Crystals */

2010-07-20T19:16:42Z

Nematic Liquid Crystals

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	<gallery widths=100px heights=200px perrow=3 align=right>		<gallery widths=100px heights=200px perrow=3 align=right>
	Image:Director_lc_plain.png‎‎\|Note the lack of positional order along the axis of the director		Image:Director_lc_plain.png‎‎\|Note the lack of positional order along the axis of the director
	Image:~~140px-~~LiquidCrystal-MesogenOrder-Nematic.jpg\|Molecules align in liquid crystal phase		Image:LiquidCrystal-MesogenOrder-Nematic.jpg\|Molecules align in liquid crystal phase
	</gallery>		</gallery>

Cmditradmin: /* Hopping Mechanism for Charge Transport */

2010-07-07T19:13:31Z

Hopping Mechanism for Charge Transport

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	=== Hopping Mechanism for Charge Transport ===		=== Hopping Mechanism for Charge Transport ===
	[[Image:Hopping_lc.png\|thumb\|~~300px~~\|]]		[[Image:Hopping_lc.png\|thumb\|400px\|Hopping transport in donor an acceptor materials]]

	In the hopping model of transport there is series of redox reactions in which electrons are transferred from site to site. This requires a good overlap between the orbitals. Discotic crystals have the ability to overlap.		In the hopping model of transport there is series of redox reactions in which electrons are transferred from site to site. This requires a good overlap between the orbitals. Discotic crystals have the ability to overlap.

Cmditradmin: /* Smectic Phases */

2010-06-23T00:06:51Z

Smectic Phases

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	Image:Smectic_A.png‎\|Smectic A are aligned along position planes.		Image:Smectic_A.png‎\|Smectic A are aligned along position planes.
	Image:Smectic_C.png\|Smectic C has an orientation offset from the position plane		Image:Smectic_C.png\|Smectic C has an orientation offset from the position plane
	Image:~~Smectic_C~~.jpg\|Smectic C liquid crystal under polarized light		Image:Fächertextur.jpg\|Smectic C liquid crystal under polarized light
	</gallery>		</gallery>

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	=== Ferroelectric Smectic C* ===		=== Ferroelectric Smectic C* ===
	[[Image:Smectic_Cstar__ferro.png\|thumb\|400px\|An applied electric field will align the dipoles of ferroelectric molecules creating a bulk dipole moment]]		[[Image:Smectic_Cstar__ferro.png\|thumb\|400px\|An applied electric field will align the dipoles of ferroelectric molecules creating a bulk dipole moment]]

Cmditradmin at 23:20, 2 September 2009

2009-09-02T23:20:59Z

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	</table>		</table>

			Liquid crystals can be classified by their behavior and by their physical structure.
			== Classification of Liquid Crystals ==

	[[Image:Classification_lc.png\|thumb\|500px\|]]		[[Image:Classification_lc.png\|thumb\|500px\|]]

Cmditradmin at 23:18, 2 September 2009

2009-09-02T23:18:45Z

← Older revision		Revision as of 16:18, 2 September 2009
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	</table>		</table>

	~~== Classification ==~~
	[[Image:Classification_lc.png\|thumb\|500px\|]]		[[Image:Classification_lc.png\|thumb\|500px\|]]
	Liquid crystals can be first organized into thermotropic (temperature dependent) and lyotropic (concentration dependent). Within thermotropic liquid crystals there are high molar mass materials (suitable for polymer) and low molar mass materials. Within the polymeric kind there are main chain polymers where the chains align in a direction, or a chain where there is comb-like structure with side chains that hang off the polymer. The director is oriented either along the main chain or parallel to the side chains.		Liquid crystals can be first organized into thermotropic (temperature dependent) and lyotropic (concentration dependent). Within thermotropic liquid crystals there are high molar mass materials (suitable for polymer) and low molar mass materials. Within the polymeric kind there are main chain polymers where the chains align in a direction, or a chain where there is comb-like structure with side chains that hang off the polymer. The director is oriented either along the main chain or parallel to the side chains.
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	~~'''~~Calamitic vs Discotic~~'''~~
			=== Calamitic vs Discotic ===

	[[Image:Cyanobiphenyls.png\|thumb\|300px\|Common molecules used to create liquid crystals. Calamitic (left) Discotic (right)]]		[[Image:Cyanobiphenyls.png\|thumb\|300px\|Common molecules used to create liquid crystals. Calamitic (left) Discotic (right)]]

Cmditradmin: /* Hopping Mechanism for Charge Transport */

2009-09-02T23:16:14Z

Hopping Mechanism for Charge Transport

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	== Charge Transport in Liquid Crystals ==		== Charge Transport in Liquid Crystals ==

			<br clear='all'>
	=== Hopping Mechanism for Charge Transport ===		=== Hopping Mechanism for Charge Transport ===
	[[Image:Hopping_lc.png\|thumb\|300px\|]]		[[Image:Hopping_lc.png\|thumb\|300px\|]]

	In the hopping model of transport there is series of redox reactions in which electrons are transferred from site to site. This requires a good overlap between the orbitals. Discotic crystals have the ability to overlap.		In the hopping model of transport there is series of redox reactions in which electrons are transferred from site to site. This requires a good overlap between the orbitals. Discotic crystals have the ability to overlap.

Cmditradmin: /* Discotic Liquid Crystals */

2009-09-02T23:15:48Z

Discotic Liquid Crystals

← Older revision		Revision as of 16:15, 2 September 2009
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	In nematic discotics phases there is no positional order between the molecules ~~but~~ only orientational order.		In nematic discotics phases there is no positional order between the molecules, only orientational order.

	In the case of columnar discotic phases the molecules themselves lie roughly on top of each other, so there is some degree of positional order. This columns of discs tend to form hexagonal patterns and these phases are called hexagonal columnar discotics. Columnar molecules can have specific shapes which cause them to line up perfectly or rotate as they fit together.		In the case of columnar discotic phases the molecules themselves lie roughly on top of each other, so there is some degree of positional order. This columns of discs tend to form hexagonal patterns and these phases are called hexagonal columnar discotics. Columnar molecules can have specific shapes which cause them to line up perfectly or rotate as they fit together.
	<br clear='all'>		<br clear='all'>
	[[Image:120px-Phthalocyanine_Green_G.png\|thumb\|300px\|A phthalocyanine]]		[[Image:120px-Phthalocyanine_Green_G.png\|thumb\|300px\|A phthalocyanine]]
	Klaus Mullen is a talented chemist at the Max Planck Institute for Polmer Science in Mainz. He has started to make graphitic type molecules based on molecules such as triphenylene, thalocyanine, and hexobenzochoridine. The common characteristic is a common pi core that is roughly flat with flexible alkyl chains on the periphery.		Klaus Mullen is a talented chemist at the Max Planck Institute for Polmer Science in Mainz. He has started to make graphitic type molecules based on molecules such as triphenylene, thalocyanine, and hexobenzochoridine. The common characteristic is a common π core that is roughly flat with flexible alkyl chains on the periphery. These molecules have been examined for use as charge transport materials.

	see Mullen 2004 <ref>http://www.rsc.org/ej/jm/2004/b312789c.pdf</ref>		see Mullen 2004 <ref>http://www.rsc.org/ej/jm/2004/b312789c.pdf</ref>


	== Charge Transport in Liquid Crystals ==		== Charge Transport in Liquid Crystals ==

Cmditradmin: /* Hopping Mechanism for Charge Transport */

2009-09-02T23:15:10Z

Hopping Mechanism for Charge Transport

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	[[Image:Hopping_lc.png\|thumb\|300px\|]]		[[Image:Hopping_lc.png\|thumb\|300px\|]]

	~~These molecules have been examined for use as charge transport materials.~~ In the hopping model of transport there is series of redox reactions in which electrons are transferred from site to site. This requires a good overlap between the orbitals. Discotic crystals have the ability to overlap.		In the hopping model of transport there is series of redox reactions in which electrons are transferred from site to site. This requires a good overlap between the orbitals. Discotic crystals have the ability to overlap.

	See [[Band Regime versus Hopping Regime]]		See [[Band Regime versus Hopping Regime]]

Cmditradmin: /* Classification */

2009-09-02T22:40:25Z

Classification

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	~~===~~ Calamitic vs Discotic ~~===~~		'''Calamitic vs Discotic'''
	[[Image:Cyanobiphenyls.png\|thumb\|300px\|Common molecules used to create liquid crystals. Calamitic (left) Discotic (right)]]		[[Image:Cyanobiphenyls.png\|thumb\|300px\|Common molecules used to create liquid crystals. Calamitic (left) Discotic (right)]]

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	The discotics such as triphenylenes can stack up but have long tails (akyl or alkoxy with C12 groups) that allow the discs to remain flexible so they do not become fully crystalline but has a discotic liquid crystal phase.		The discotics such as triphenylenes can stack up but have long tails (akyl or alkoxy with C12 groups) that allow the discs to remain flexible so they do not become fully crystalline but has a discotic liquid crystal phase.


	== Calamitic Liquid Crystals ==		== Calamitic Liquid Crystals ==

Cmditradmin: /* Smectic Phases */

2009-09-02T22:38:00Z

Smectic Phases

← Older revision		Revision as of 15:38, 2 September 2009
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	The pitch is very sensitive to temperature and accordingly, cholesteric LC have temperature dependent optical properties--remember mood rings		The pitch is very sensitive to temperature and accordingly, cholesteric LC have temperature dependent optical properties--remember mood rings

	== Smectic Phases ==		=== Smectic Phases ===
	<gallery widths=100px heights=200px perrow=3 align =right>		<gallery widths=100px heights=200px perrow=3 align =right>
	Image:Smectic_A.png‎\|Smectic A are aligned along position planes.		Image:Smectic_A.png‎\|Smectic A are aligned along position planes.