Mbiri Yofufuzira
Monga chuma chachilengedwe, chochuluka komanso chobwezerezedwanso, cellulose imakumana ndi zovuta zazikulu pakugwiritsa ntchito chifukwa cha mphamvu zake zosasungunuka komanso zochepa zosungunulira. Ma crystallinity apamwamba komanso ma hydrogen bond apamwamba mu kapangidwe ka cellulose zimapangitsa kuti iwonongeke koma isasungunuke panthawi yogwiritsidwa ntchito, komanso isasungunuke m'madzi ndi zinthu zambiri zachilengedwe. Zotumphukira zawo zimapangidwa ndi esterification ndi etherification ya magulu a hydroxyl pamayunitsi a anhydroglucose mu unyolo wa polymer, ndipo zidzawonetsa makhalidwe osiyanasiyana poyerekeza ndi cellulose yachilengedwe. Kuyankha kwa etherification kwa cellulose kumatha kupanga ma ether ambiri a cellulose osungunuka m'madzi, monga methyl cellulose (MC), hydroxyethyl cellulose (HEC) ndi hydroxypropyl cellulose (HPC), omwe amagwiritsidwa ntchito kwambiri muzakudya, zodzoladzola, zamankhwala ndi zamankhwala. CE yosungunuka m'madzi imatha kupanga ma polima olumikizidwa ndi hydrogen ndi ma polycarboxylic acid ndi ma polyphenols.
Kusonkhana kwa magawo ndi magawo (LBL) ndi njira yothandiza yokonzekera mafilimu opyapyala a polymer. Izi zikufotokoza makamaka za kusonkhana kwa LBL kwa ma CE atatu osiyanasiyana a HEC, MC ndi HPC ndi PAA, kuyerekeza momwe amagwirira ntchito, ndikusanthula momwe zinthu zina zimakhudzira kusonkhana kwa LBL. Fufuzani momwe pH imakhudzira makulidwe a filimu, ndi kusiyana kosiyana kwa pH pakupanga ndi kusungunuka kwa filimu, ndikukulitsa mphamvu zoyamwa madzi za CE/PAA.
Zipangizo Zoyesera:
Polyacrylic acid (PAA, Mw = 450,000). Kukhuthala kwa yankho lamadzi la 2wt.% la hydroxyethylcellulose (HEC) ndi 300 mPa·s, ndipo mlingo wosinthira ndi 2.5. Methylcellulose (MC, yankho lamadzi la 2wt.% lokhala ndi kukhuthala kwa 400 mPa·s ndi digiri yosinthira ya 1.8). Hydroxypropyl cellulose (HPC, yankho lamadzi la 2wt.% lokhala ndi kukhuthala kwa 400 mPa·s ndi digiri yosinthira ya 2.5).
Kukonzekera filimu:
Yokonzedwa ndi madzi oundana a crystal layer assembly pa silicon pa 25°C. Njira yochizira ya slide matrix ndi iyi: ilowetseni mu acidic solution (H2SO4/H2O2, 7/3Vol/VOL) kwa mphindi 30, kenako muzimutsuka ndi madzi oyeretsedwa kangapo mpaka pH itakhala yopanda mbali, kenako iume ndi nayitrogeni yeniyeni. LBL assembly imachitika pogwiritsa ntchito makina odzipangira okha. Substrate inalowetsedwa mosinthana mu CE solution (0.2 mg/mL) ndi PAA solution (0.2 mg/mL), yankho lililonse linalowetsedwa kwa mphindi 4. Kuthira katatu kwa mphindi 1 m'madzi oyeretsedwa kunachitidwa pakati pa yankho lililonse kuti muchotse polymer yolumikizidwa momasuka. pH values ya assembly solution ndi assuring solution zonse zinasinthidwa kukhala pH 2.0. Mafilimu okonzedwa amatchulidwa kuti (CE/PAA)n, pomwe n imasonyeza kuzungulira kwa assembly. (HEC/PAA)40, (MC/PAA)30 ndi (HPC/PAA)30 makamaka anakonzedwa.
Kufotokozera za Mafilimu:
Ma spectra owunikira omwe ali pafupi ndi nthawi zonse adajambulidwa ndikusanthulidwa ndi NanoCalc-XR Ocean Optics, ndipo makulidwe a mafilimu omwe adayikidwa pa silicon adayesedwa. Ndi substrate yopanda kanthu ya silicon ngati maziko, sipekitiramu ya FT-IR ya filimu yopyapyala pa substrate ya silicon idasonkhanitsidwa pa Nicolet 8700 infrared spectrometer.
Kugwirizana kwa ma hydrogen bond pakati pa PAA ndi CEs:
Kusonkhanitsa HEC, MC ndi HPC ndi PAA mu mafilimu a LBL. Ma spectra a infrared a HEC/PAA, MC/PAA ndi HPC/PAA akuwonetsedwa pachithunzichi. Zizindikiro zamphamvu za IR za PAA ndi CES zitha kuwoneka bwino mu ma spectra a IR a HEC/PAA, MC/PAA ndi HPC/PAA. Ma spectroscopy a FT-IR amatha kusanthula complexation ya hydrogen bond pakati pa PAA ndi CES poyang'anira kusintha kwa ma absorption bands. Kugwirizana kwa hydrogen pakati pa CES ndi PAA kumachitika makamaka pakati pa hydroxyl oxygen ya CES ndi gulu la COOH la PAA. Pambuyo poti hydrogen bond yapangidwa, stretching peak red imasunthira ku low frequency direction.
Panali nsonga ya 1710 cm-1 ya ufa wa PAA wokha. Pamene polyacrylamide inasonkhanitsidwa m'mafilimu okhala ndi ma CE osiyanasiyana, nsonga za mafilimu a HEC/PAA, MC/PAA ndi MPC/PAA zinali pa 1718 cm-1, 1720 cm-1 ndi 1724 cm-1, motsatana. Poyerekeza ndi ufa wa PAA wokha, kutalika kwa nsonga za mafilimu a HPC/PAA, MC/PAA ndi HEC/PAA kunasinthidwa ndi 14, 10 ndi 8 cm-1, motsatana. Chigwirizano cha haidrojeni pakati pa ether oxygen ndi COOH chimasokoneza mgwirizano wa haidrojeni pakati pa magulu a COOH. Ma bond a haidrojeni ambiri akapangidwa pakati pa PAA ndi CE, kusintha kwa nsonga kwa CE/PAA mu IR spectra kumakulirakulira. HPC ili ndi kuchuluka kwakukulu kwa hydrogen bond complexation, PAA ndi MC zili pakati, ndipo HEC ndiye yotsika kwambiri.
Kukula kwa mafilimu ophatikizika a PAA ndi CEs:
Khalidwe la PAA ndi CEs popanga mafilimu panthawi ya LBL assembly linafufuzidwa pogwiritsa ntchito QCM ndi spectral interferometry. QCM ndi yothandiza poyang'anira kukula kwa filimu pamalo oyamba pa nthawi yochepa yopangira mafilimu. Ma spectral interferometers ndi oyenera mafilimu omwe amakula kwa nthawi yoposa 10.
Filimu ya HEC/PAA inawonetsa kukula kolunjika panthawi yonse yopangira LBL, pomwe mafilimu a MC/PAA ndi HPC/PAA adawonetsa kukula kwakukulu kumayambiriro kwa kupanga kenako nkusintha kukhala kukula kolunjika. Mu gawo la kukula kolunjika, kuchuluka kwa kusinthasintha kwa mawonekedwe, kukula kwa makulidwe kumakulirakulira pa nthawi iliyonse yopangira.
Zotsatira za pH ya yankho pa kukula kwa filimu:
Kuchuluka kwa pH kwa yankho kumakhudza kukula kwa filimu ya polymer yolumikizidwa ndi hydrogen. Monga polyelectrolyte yofooka, PAA idzasinthidwa kukhala ion ndi kuyikidwa pansi pa mphamvu pamene pH ya yankho ikukwera, motero kuletsa mgwirizano wa hydrogen bond. Pamene mlingo wa ionization wa PAA wafika pamlingo winawake, PAA singathe kusonkhana kukhala filimu yokhala ndi zolandirira hydrogen bond mu LBL.
Kukhuthala kwa filimu kunachepa ndi kuwonjezeka kwa pH ya yankho, ndipo makulidwe a filimuyo anachepa mwadzidzidzi pa pH2.5 HPC/PAA ndi pH3.0-3.5 HPC/PAA. Mfundo yofunika kwambiri ya HPC/PAA ndi pafupifupi pH 3.5, pomwe ya HEC/PAA ndi pafupifupi 3.0. Izi zikutanthauza kuti pamene pH ya yankho losonkhanitsira ili pamwamba pa 3.5, filimu ya HPC/PAA singapangidwe, ndipo pamene pH ya yankho ili pamwamba pa 3.0, filimu ya HEC/PAA singapangidwe. Chifukwa cha kuchuluka kwa hydrogen bond complexation ya nembanemba ya HPC/PAA, pH yofunika kwambiri ya nembanemba ya HPC/PAA ndi yapamwamba kuposa ya nembanemba ya HEC/PAA. Mu yankho lopanda mchere, pH yofunika kwambiri ya ma complexes opangidwa ndi HEC/PAA, MC/PAA ndi HPC/PAA inali pafupifupi 2.9, 3.2 ndi 3.7, motsatana. pH yofunika kwambiri ya HPC/PAA ndi yokwera kuposa ya HEC/PAA, zomwe zimagwirizana ndi ya nembanemba ya LBL.
Kugwira ntchito kwa nembanemba ya CE/PAA kuyamwa madzi:
CES ili ndi magulu ambiri a hydroxyl kotero kuti imayamwa bwino madzi komanso imasunga madzi. Potengera chitsanzo cha nembanemba ya HEC/PAA, mphamvu ya kuyamwa kwa nembanemba ya CE/PAA yolumikizidwa ndi hydrogen kupita kumadzi m'chilengedwe idaphunziridwa. Podziwika ndi spectral interferometry, makulidwe a filimuyi amawonjezeka pamene filimuyi ikuyamwa madzi. Inayikidwa pamalo okhala ndi chinyezi chosinthika pa 25°C kwa maola 24 kuti ikwaniritse kuyamwa kwa madzi. Mafilimuwa anaumitsidwa mu uvuni wa vacuum (40°C) kwa maola 24 kuti achotse chinyezi chonse.
Pamene chinyezi chikuwonjezeka, filimuyo imakhuthala. Pamalo ocheperako a chinyezi cha 30%-50%, makulidwe ake amachepa. Chinyezi chikapitirira 50%, makulidwe ake amakula mofulumira. Poyerekeza ndi nembanemba ya PPVON/PAA yolumikizidwa ndi hydrogen, nembanemba ya HEC/PAA imatha kuyamwa madzi ambiri kuchokera ku chilengedwe. Pansi pa chinyezi cha 70% (25°C), kuchuluka kwa makulidwe a filimu ya PPVON/PAA ndi pafupifupi 4%, pomwe filimu ya HEC/PAA ndi yokwera pafupifupi 18%. Zotsatira zake zasonyeza kuti ngakhale kuti magulu ena a OH mu HEC/PAA system adatenga nawo gawo pakupanga ma hydrogen bonds, panali magulu ambiri a OH omwe amalumikizana ndi madzi m'chilengedwe. Chifukwa chake, HEC/PAA system ili ndi mphamvu zabwino zoyamwa madzi.
Pomaliza
(1) Dongosolo la HPC/PAA lomwe lili ndi digiri yapamwamba kwambiri ya hydrogen bonding ya CE ndi PAA lili ndi kukula kwachangu kwambiri pakati pawo, MC/PAA ili pakati, ndipo HEC/PAA ndi yotsika kwambiri.
(2) Filimu ya HEC/PAA inawonetsa njira yokulira yolunjika panthawi yonse yokonzekera, pomwe mafilimu ena awiri a MC/PAA ndi HPC/PAA adawonetsa kukula kwakukulu m'magawo oyamba, kenako nkusinthidwa kukhala njira yokulira yolunjika.
(3) Kukula kwa filimu ya CE/PAA kumadalira kwambiri pH ya yankho. Pamene pH ya yankho ili pamwamba kuposa mfundo yake yofunika, PAA ndi CE sizingasonkhanitsidwe kukhala filimu. Nembanemba ya CE/PAA yosonkhanitsidwayo inali yosungunuka mu njira zothetsera pH zambiri.
(4) Popeza filimu ya CE/PAA ili ndi OH ndi COOH zambiri, chithandizo cha kutentha chimapangitsa kuti ikhale yolumikizidwa. Nembanemba ya CE/PAA yolumikizidwa ili ndi kukhazikika kwabwino ndipo siisungunuka mu njira zoyezera pH zambiri.
(5) Filimu ya CE/PAA ili ndi mphamvu yabwino yothira madzi m'chilengedwe.
Nthawi yotumizira: Feb-18-2023