liquid crystal liquid crystals matter state properties conventional solid crystals instance liquid crystal flow like liquid molecules oriented crystal like way different types liquid crystal phases distinguished different optical properties viewed microscope light source different liquid crystal phases appear distinct textures contrasting areas textures correspond domains liquid crystal molecules oriented different directions domain molecules ordered materials liquid crystal phase water turn ice steam liquid crystals divided phases liquid crystals consist organic molecules minerals known exhibit phase transition liquid crystal phase temperature changed exhibit phase transitions function temperature concentration liquid crystal molecules typically water composed organic molecules liquid crystal transition depends temperature concentration organic composition ratio examples liquid crystals found natural world technological applications contemporary electronic displays use liquid crystals liquid phases abundant living systems found mineral world example proteins cell membranes liquid crystals known examples liquid crystals solutions soap related tobacco mosaic virus history austrian botanical working examined chemical properties derivatives belong class materials known liquid crystals previously researchers observed distinct color effects cooling derivatives freezing point associated new phenomenon perceived color changes derivative peculiar feature found melt manner compounds melting points cloudy liquid cloudy liquid clear phenomenon seeking help physicist march wrote time exchanged letters samples examined intermediate cloudy fluid reported seeing colleague indicated intermediate fluid exchange letters ended april questions unanswered presented results credits meeting time discovered described important features liquid crystals coined existence melting points reflection light ability rotate direction light accidental discovery pursue studying liquid crystals research continued realized encountered new phenomenon position investigate years acquired expertise started systematic study related compounds exhibited double melting phenomenon able observations light microscope equipped hot stage sample holder equipped enabling high temperature observations intermediate cloudy phase clearly sustained flow features particularly signature microscope convinced dealing solid end august published results work continued significantly expanded german chemist beginning 20th century retirement synthesized liquid crystals known liquid crystals popular scientists material remained pure scientific curiosity years world war work synthesis liquid crystals restarted university research laboratories europe prominent researcher liquid crystals began investigating materials england late 1940s group synthesized new materials exhibited liquid state developed better understanding design molecules exhibit state book molecular structure properties liquid crystals subject study liquid crystals starting later organized international conference liquid crystals kent ohio world liquid crystal scientists attendance conference marked beginning worldwide effort perform research field soon led development practical applications unique materials liquid crystal materials focus research development flat panel electronic displays beginning physical chemist applied electric field thin layer liquid crystal observed formation regular pattern called domains known led colleague perform research liquid crystal based flat panel display replace ray vacuum tube williams exhibits liquid crystal state impractical use commercial display product material operated room temperature clearly needed research group discovered exclusively compounds differed number carbon terminal chains yield room temperature liquid crystals mixture base compounds resulted material range operation room temperature enabled practical display device team proceeded prepare numerous compounds lower melting points technique mixing compounds obtain wide operating temperature range eventually industry standard day tailor materials meet specific applications succeeded substance phase room temperature popular subjects liquid crystal research step liquid crystal displays synthesis stable substances low melting temperatures work led design new materials resulting rapid adoption small area electronic products molecules rod shaped created lab appear spontaneously nature new types molecules discovered man disc shaped created group india bowl shaped invented china synthesized europe years later liquid crystal displays established working received nobel prize physics discovering methods developed studying order phenomena simple systems complex forms matter particular liquid crystals design liquid materials large number chemical compounds known exhibit liquid phases despite significant differences chemical composition molecules common features chemical physical properties types liquid crystals rod shaped molecules flat disc like molecules consisting core adjacent rings core flat like rice bowl dimensional object allows dimensional ordering rod shaped molecules elongated geometry allows alignment spatial direction molecular shape relatively thin flat bowl like especially rigid molecular molecular length consistent presence long group room temperature liquid crystals structure branched angular low melting point order avoid liquid phases low temperature behavior general useful terminal groups promote extended structurally rigid highly shape main criterion liquid behavior result liquid materials based rings liquid crystal phases liquid crystal phases called characterized type ordering distinguish order molecules arranged sort ordered order molecules pointing direction order short range molecules close long range extending larger dimensions phase high temperature heating eventually drive conventional liquid phase characterized random molecular ordering little long range order fluid like flow behavior conditions instance lower temperature inhabit phases significant structure short range order having ability flow ordering liquid phases extensive molecular scale order extends entire domain size order usually extend scale occurs classical techniques use boundaries applied electric field enforce single ordered domain liquid crystal sample ordering liquid crystal extend dimension material essentially directions liquid crystals phases occur certain temperature range temperature rise high thermal motion destroy delicate cooperative ordering phase pushing material conventional liquid phase low temperature materials form conventional crystal exhibit variety phases temperature changed instance heating particular type called exhibit phases followed phase finally phase temperature increased example compound displaying behavior phase common phases word comes greek greek means thread term originates thread like defects observed formally called exhibit called defects phase rod shaped organic molecules order self align long range directional order long axes roughly parallel molecules free flow center mass positions randomly distributed liquid maintain long range directional order axis longer preferred equivalent cylinders rods liquid crystals meaning addition long axis orient secondary axis similar ordinary easily aligned external magnetic electric field aligned optical properties crystals makes extremely useful liquid crystal displays phases phases found lower temperatures form defined layers slide manner similar soap word originates latin word meaning cleaning having soap like properties ordered direction phase molecules oriented layer normal phase away phases liquid like layers different phases characterized different types degrees order phases phase exhibits phase called phase observed derivatives molecules internal planes symmetry rise phase phase exhibits twisting molecules perpendicular director molecular axis parallel director finite twist angle adjacent molecules packing results longer range order phase denotes phase molecules ordering layered structure phases molecules finite angle respect layer normal finite twist layer producing spiral twisting molecular axis layer normal pitch refers distance molecules undergo twist note structure phase repeats half pitch phase directors equivalent pitch typically changes temperature altered molecules added host host material form phase material allowing pitch given material tuned accordingly liquid crystal systems pitch order visible light causes systems exhibit unique optical properties reflection low threshold laser properties exploited number optical applications case reflection lowest order reflection allowed light incident axis oblique higher order reflections permitted liquid crystals exhibit unique property reflect light incident axis comes blue phases liquid crystal phases appear temperature range phase liquid phase blue phases regular dimensional cubic structure defects periods exhibit selective reflections range visible light corresponding cubic theoretically predicted phases possess symmetry similar blue phases interest fast light crystals exist narrow temperature range usually recently blue phases temperature range including room temperature demonstrated blue phases stabilized room temperature allow electro optical switching response times order blue phase mode panel developed phases disk shaped molecules orient layer like fashion known phase pack phase called columns organized rectangular phases similar phase known phases bowl shaped molecules like form phases phases polar phases predicted phases polar phases liquid crystals liquid crystal consists components exhibit liquid properties certain concentration ranges phases molecules fill space compounds provide system contrast liquid crystals degree freedom concentration enables induce variety different phases compound parts called molecules liquid phase sequences depending volume structures formed micro phase segregation incompatible components scale soap everyday example liquid crystal content water molecules changes self assembled structures low concentration molecules dispersed randomly ordering slightly higher low concentration molecules spontaneously assemble hide tail inside core exposing water surface solution spherical objects order solution higher concentration assemblies ordered typical phase phase form long cylinders surface arrange roughly called middle soap phase higher concentration phase neat soap phase form extended sheets separated thin layers water systems cubic called phase exist phases spheres formed create dense cubic spheres connected forming cubic phase objects created usually spherical case disc like rod like axes distinct self assembled structures order way liquid crystals forming large scale versions phases phase rod shaped systems high concentrations phases observed generate phase columns water phase bulk liquid crystal sample spherical water generic progression phases going low high concentration cubic phase cubic phase phase phase middle phase phase cubic phase reverse phase cubic phase phase phases self assembled structures concentration example phases layer distances increase volume liquid crystals rely subtle balance interactions difficult analyze structures properties liquid crystals similar phases characteristics observed liquid crystals liquid crystal phases based low melting phases like structure formed linked easily form glasses addition long chain soap like molecules leads series new phases variety liquid behavior function organic composition ratio temperature class materials named laboratory analysis detected characterized major methods original method use thermal optical small sample material placed crossed sample heated cooled phase significantly affect light appear dark crystal liquid crystal phases light uniform way leading color method allows characterization particular phase different phases defined particular order observed second method differential scanning allows precise determination phase transitions transition small sample heated way generates precise change temperature respect time phase transitions heat flow required maintain heating cooling rate change changes observed attributed phase transitions key liquid crystal transitions analyzed similar fashion experiments somewhat complex concentration key factor experiments run concentrations order analyze impact biological liquid crystals liquid phases abundant living systems study referred accordingly liquid crystals attract particular attention field chemistry particular biological membranes cell membranes form liquid crystal constituent molecules perpendicular membrane surface membrane flexible vary shape page constituent molecules inter easily tend leave membrane high energy requirement process molecules flip membrane process depending direction movement liquid crystal membrane phases host important proteins freely floating inside partly outside membrane biological structures exhibit liquid crystal behavior instance concentrated protein solution spider generate silk fact liquid crystal phase precise ordering molecules silk critical renowned strength dna form phases forms important current academic research mineral liquid crystals examples liquid crystals found mineral world discovered discovered studied details existence true phase case family raised remained open long time solved recently rapid development synthesis new number mineral liquid crystals quickly increasing example carbon phase discovered exhibit distance pattern formation liquid crystals liquid crystals property observed makes flows liquid crystals behave ordinary example injection liquid crystal close parallel plates causes orientation molecules couple flow resulting emergence patterns manifested energy surface tension different liquid crystal phases determines shape temperature strong usually appear temperature changed phases grows forming different depending temperature change growth controlled heat thermal favors growth specific directions effect final shape theoretical treatment liquid crystals microscopic theoretical treatment fluid phases complicated owing high material density meaning strong interactions hard core body ignored case liquid crystals interactions analysis number fairly simple theories predict general behavior phase transitions liquid crystal systems director saw liquid crystals composed rod like molecules long axes neighboring molecules aligned approximately describe structure unit called director introduced represent direction preferred orientation molecules neighborhood point physical director axis fully equivalent order description liquid crystals involves analysis order second rank order describe order liquid crystal order usually sufficient describe liquid crystals order usually defined based average second formula formula angle liquid crystal molecular axis local director preferred direction volume element liquid crystal sample representing local optical axis denote temporal spatial average definition convenient completely random sample perfectly aligned sample typical liquid crystal sample order generally decreases temperature raised particular sharp drop order observed system undergoes phase transition phase phase order measured number ways instance scattering determine order liquid crystal characterized odd average zero director point directions higher order averages difficult measure yield additional information molecular ordering order describe ordering liquid crystal characterized variation density center mass liquid crystal molecules given case variation axis density formula given formula complex order defined formula formula average density typically terms kept higher order terms ignored phases described adequately functions perfect formula phase formula complex values complex nature order allows parallels phase transitions conductor transitions hard rod model simple model phase transitions hard rod model proposed theory considers volume excluded center mass cylinder approaches specifically cylinders oriented parallel little volume excluded center mass approaching cylinder come close cylinder cylinders angle large volume surrounding cylinder approaching cylinder center mass enter hard rod objects angular arrangement sees decrease net approaching cylinder fewer states available fundamental insight whilst parallel arrangements objects lead decrease increase case greater order favorable theory solution rod shaped objects undergo phase transition sufficient concentration phase model helpful mathematical makes assumptions limit real systems mean field theory statistical theory proposed includes contributions attractive potential induced moment adjacent liquid crystal molecules attraction parallel alignment neighboring molecules theory considers mean field average interaction solved self consistently theory phase transitions consistent experiment model model proposed extension mean field theory describe phase transition liquid crystal phase phase transition continuous depending strength short range interaction molecules result allows triple critical point phase meet existence triple critical point successfully predict value model utilizes order parameters describe order liquid crystal simply average second second order given formula values position angle molecular axis director layer potential energy single given formula constant strength interaction adjacent molecules potential derive properties system assuming thermal results self consistency solved numerically solutions stable phases liquid crystal elastic theory liquid crystal material treated molecular details entirely ignored theory considers presumed oriented sample liquid crystal commonly described frank free energy density identify types occur oriented sample twists material neighboring molecules forced angled respect aligned material bending occurs perpendicular director bend material distortion parallel director molecular axis types energy penalty induced boundary conditions domain walls container response material terms based elastic corresponding types elastic theory particularly powerful tool modeling liquid crystal devices external influences liquid crystals scientists engineers able use liquid crystals variety applications external cause significant changes properties liquid crystal system electric magnetic fields induce changes magnitude fields speed molecules align important characteristics industry deals special surface treatments liquid crystal devices force specific director electric magnetic field effects ability director align external field caused electric nature molecules permanent electric result end net positive charge end net negative charge external electric field applied liquid crystal molecules tend orient direction field form permanent influenced electric field cases field produces slight arrangement molecules induced electric results strong permanent orientation external field occurs effects magnetic fields liquid crystal molecules analogous electric fields magnetic fields generated moving electric charges permanent magnetic produced moving magnetic field applied molecules tend align field surface preparations absence external field director liquid crystal free point direction possible force director point specific direction introducing outside agent system example thin coating usually spread glass substrate single direction cloth observed liquid crystal molecules contact surface align direction currently accepted mechanism believed growth liquid crystal layers partially aligned chains near surface layers transition competition orientation produced surface electric field effects exploited liquid crystal devices consider case liquid crystal molecules aligned parallel surface electric field applied perpendicular cell electric field increases magnitude change alignment occurs threshold magnitude electric field occurs occurs director changes orientation occurrence change aligned deformed state called transition produced application magnetic field sufficient strength transition fundamental operation liquid crystal displays director orientation properties controlled easily application field effect described liquid crystal molecules usually rise means possess form usually center additional requirement system mixture left handed molecules cancel effect cooperative nature liquid crystal ordering small select domain making system overall phases usually twisting molecules pitch twist order visible light interesting optical interference effects observed twisting occurs phases makes system respond differently left handed light materials filters possible molecules produce essentially instance certain ranges concentration molecular weight dna form line phase interesting recent observation formation molecules specifically bent core molecules called banana liquid crystals shown form liquid crystal phases particular sample domains opposite given domain strong ordering present appearance mechanism entirely clear appears molecules stack layers orient fashion inside layers liquid crystals phases anti interest applications incorporated phase adding form twisted super twisted contain small applications liquid crystals liquid crystals find wide use liquid crystal displays rely optical properties certain liquid substances presence absence electric field typical device liquid crystal layer typically thick sits crossed oriented liquid crystal alignment chosen relaxed phase twisted twisted field effect twisted phase light passed allowing transmission second reflected observer provided device appears transparent electric field applied layer long molecular axes tend align parallel electric field gradually center liquid crystal layer state molecules light light absorbed second device loses transparency increasing voltage way electric field switch transparent command color systems use technique color filters generate red green blue liquid crystals fast switching light similar principles liquid crystal based optical devices liquid crystal filters devices imaging pitch varies strongly temperature crude liquid crystal color material change pitch changed liquid crystal color transitions pool liquid crystal materials change color stretched stressed liquid crystal sheets industry look hot spots map heat flow measure stress distribution patterns liquid crystal fluid form detect electrically generated hot spots failure analysis industry liquid crystal use liquid crystal medium distributed feedback mechanism instead external mirrors created periodic structure liquid crystal gives low threshold high output device stable dispersed liquid crystal sheets rolls available backed smart film applied windows electrically switched transparent provide privacy common water fact liquid crystals soap forms variety phases depending concentration water columns fast switches
Liquid crystal