Kev tshawb fawb keeb kwm
Raws li ib qho khoom siv ntuj tsim, nplua nuj thiab rov ua dua tshiab, cellulose ntsib cov teeb meem loj hauv kev siv tswv yim vim nws cov khoom tsis yaj thiab cov khoom solubility tsawg. Lub siab crystallinity thiab high-density hydrogen bonds hauv cellulose qauv ua rau nws degrade tab sis tsis yaj thaum lub sij hawm muaj txheej txheem, thiab insoluble nyob rau hauv dej thiab feem ntau organic solvents. Lawv derivatives yog tsim los ntawm esterification thiab etherification ntawm hydroxyl pawg ntawm cov anhydroglucose units nyob rau hauv lub polymer saw, thiab yuav nthuav tawm ib co txawv zog piv nrog ntuj cellulose. Cov tshuaj tiv thaiv etherification ntawm cellulose tuaj yeem tsim muaj ntau cov dej-soluble cellulose ethers, xws li methyl cellulose (MC), hydroxyethyl cellulose (HEC) thiab hydroxypropyl cellulose (HPC), uas tau siv dav hauv zaub mov, tshuaj pleev ib ce, hauv tshuaj thiab tshuaj. Dej-soluble CE tuaj yeem tsim hydrogen-bonded polymers nrog polycarboxylic acids thiab polyphenols.
Layer-by-layer assembly (LBL) yog ib txoj hauv kev zoo rau kev npaj cov polymer sib xyaw nyias zaj duab xis. Cov hauv qab no feem ntau piav qhia txog LBL lub rooj sib txoos ntawm peb qhov sib txawv CEs ntawm HEC, MC thiab HPC nrog PAA, sib piv lawv cov cwj pwm sib dhos, thiab txheeb xyuas qhov cuam tshuam ntawm cov neeg hloov pauv ntawm LBL sib dhos. Tshawb xyuas cov txiaj ntsig ntawm pH ntawm cov yeeb yaj kiab tuab, thiab qhov sib txawv ntawm pH ntawm kev tsim thiab kev sib cais, thiab txhim kho cov dej nqus dej ntawm CE / PAA.
Cov khoom siv sim:
Polyacrylic acid (PAA, Mw = 450,000). Lub viscosity ntawm 2wt.% aqueous tov ntawm hydroxyethylcellulose (HEC) yog 300 mPa·s, thiab cov degree ntawm kev hloov yog 2.5. Methylcellulose (MC, 2wt.% aqueous tov nrog viscosity ntawm 400 mPa·s thiab degree ntawm kev hloov ntawm 1.8). Hydroxypropyl cellulose (HPC, 2wt.% aqueous tov nrog viscosity ntawm 400 mPa·s thiab qib hloov ntawm 2.5).
Kev npaj ua yeeb yaj kiab:
Npaj los ntawm kua siv lead ua txheej los ua ke ntawm silicon ntawm 25 ° C. Txoj kev kho ntawm tus swb matrix yog raws li nram no: soak hauv acidic tov (H2SO4 / H2O2, 7/3Vol / VOL) rau 30min, ces yaug nrog dej deionized ob peb zaug kom txog rau thaum lub pH ua nruab nrab, thiab thaum kawg qhuav nrog ntshiab nitrogen. LBL sib dhos yog ua los ntawm cov tshuab tsis siv neeg. Lub substrate tau hloov pauv hauv cov tshuaj CE (0.2 mg / mL) thiab PAA daws (0.2 mg / mL), txhua cov tshuaj tau tsau rau 4 min. Peb yaug soaks ntawm 1 min txhua hauv dej deionized tau ua ntawm txhua qhov kev daws teeb meem kom tshem tawm cov ntaub nplaum uas txuas nrog polymer. Cov pH qhov tseem ceeb ntawm cov tshuaj sib dhos thiab cov tshuaj yaug tau raug kho rau pH 2.0. Cov yeeb yaj kiab uas tau npaj tau raug suav hais tias yog (CE/PAA)n, qhov twg n qhia txog lub voj voog sib dhos. (HEC/PAA)40, (MC/PAA)30 thiab (HPC/PAA)30 tau npaj ua ntej.
Film Characterization:
Qhov ze-zoo li qub spectra raug kaw thiab soj ntsuam nrog NanoCalc-XR Ocean Optics, thiab cov tuab ntawm cov yeeb yaj kiab tso rau ntawm silicon raug ntsuas. Nrog ib qho dawb paug silicon substrate raws li keeb kwm yav dhau, FT-IR spectrum ntawm nyias zaj duab xis ntawm silicon substrate tau sau rau ntawm Nicolet 8700 infrared spectrometer.
Hydrogen bond kev sib cuam tshuam ntawm PAA thiab CEs:
Kev sib dhos ntawm HEC, MC thiab HPC nrog PAA rau hauv LBL films. Lub infrared spectra ntawm HEC / PAA, MC / PAA thiab HPC / PAA yog pom nyob rau hauv daim duab. Cov cim IR muaj zog ntawm PAA thiab CES tuaj yeem pom meej hauv IR spectra ntawm HEC/PAA, MC/PAA thiab HPC/PAA. FT-IR spectroscopy tuaj yeem txheeb xyuas cov hydrogen bond complexation ntawm PAA thiab CES los ntawm kev saib xyuas cov kev hloov ntawm cov cwj pwm nqus cov qhab. Kev sib txuas ntawm hydrogen ntawm CES thiab PAA feem ntau tshwm sim ntawm hydroxyl oxygen ntawm CES thiab COOH pawg PAA. Tom qab lub hydrogen daim ntawv cog lus yog tsim, lub stretching ncov liab hloov mus rau qhov tsawg zaus kev taw qhia.
Lub ncov ntawm 1710 cm-1 tau pom rau cov hmoov PAA ntshiab. Thaum polyacrylamide tau sib sau ua ke rau hauv cov yeeb yaj kiab nrog cov CEs sib txawv, lub ncov ntawm HEC / PAA, MC / PAA thiab MPC / PAA cov yeeb yaj kiab tau nyob ntawm 1718 cm-1, 1720 cm-1 thiab 1724 cm-1, raws li. Piv nrog cov hmoov PAA ntshiab, lub ncov ntev ntawm HPC / PAA, MC / PAA thiab HEC / PAA cov yeeb yaj kiab hloov los ntawm 14, 10 thiab 8 cm-1, feem. Cov hydrogen bond ntawm ether oxygen thiab COOH cuam tshuam cov hydrogen bond ntawm COOH pawg. Qhov ntau hydrogen bonds tsim ntawm PAA thiab CE, qhov ntau dua qhov siab tshaj ntawm CE / PAA hauv IR spectra. HPC muaj qhov siab tshaj plaws ntawm hydrogen bond complexation, PAA thiab MC nyob nruab nrab, thiab HEC yog qhov qis tshaj.
Kev loj hlob tus cwj pwm ntawm cov yeeb yaj kiab sib xyaw ntawm PAA thiab CEs:
Tus cwj pwm ua yeeb yaj kiab ntawm PAA thiab CEs thaum lub sij hawm LBL sib dhos tau tshawb xyuas siv QCM thiab spectral interferometry. QCM muaj txiaj ntsig zoo rau kev saib xyuas cov yeeb yaj kiab loj hlob hauv qhov chaw thaum thawj ob peb lub voj voog sib dhos. Spectral interferometers yog tsim rau cov yeeb yaj kiab loj tshaj 10 lub voj voog.
HEC / PAA zaj duab xis tau qhia txog kev loj hlob nyob rau hauv cov txheej txheem LBL sib dhos, thaum MC / PAA thiab HPC / PAA cov yeeb yaj kiab tau qhia txog kev loj hlob ntawm cov theem pib ntawm kev sib dhos thiab tom qab ntawd hloov mus rau hauv kev loj hlob. Nyob rau hauv cheeb tsam kev loj hlob linear, siab dua cov degree ntawm complexation, qhov ntau dua qhov thickness loj hlob ib lub voj voog sib dhos.
Cov nyhuv ntawm cov tshuaj pH ntawm kev loj hlob ntawm zaj duab xis:
Tus nqi pH ntawm cov tshuaj cuam tshuam rau kev loj hlob ntawm hydrogen bonded polymer composite zaj duab xis. Raws li ib tug tsis muaj zog polyelectrolyte, PAA yuav ionized thiab tsis zoo nqi raws li cov pH ntawm cov tshuaj nce, yog li inhibiting hydrogen bond koom haum. Thaum lub degree ntawm ionization ntawm PAA mus txog ib theem, PAA tsis tuaj yeem sib sau ua ib zaj duab xis nrog hydrogen daim ntawv cog lus lees txais hauv LBL.
Cov yeeb yaj kiab tuab tau txo qis nrog qhov nce ntawm cov tshuaj pH, thiab cov yeeb yaj kiab thickness poob sai sai ntawm pH2.5 HPC / PAA thiab pH3.0-3.5 HPC / PAA. Lub ntsiab lus tseem ceeb ntawm HPC / PAA yog hais txog pH 3.5, thaum lub HEC / PAA yog li 3.0. Qhov no txhais tau hais tias thaum pH ntawm cov kev daws teeb meem siab dua 3.5, HPC / PAA zaj duab xis tsis tuaj yeem tsim, thiab thaum pH ntawm cov tshuaj sib tov siab dua 3.0, HEC / PAA zaj duab xis tsis tuaj yeem tsim. Vim tias qhov siab dua ntawm hydrogen bond complexation ntawm HPC / PAA daim nyias nyias, tus nqi pH tseem ceeb ntawm HPC / PAA daim nyias nyias yog siab dua li ntawm HEC / PAA membrane. Hauv kev daws cov ntsev tsis muaj ntsev, qhov tseem ceeb pH qhov tseem ceeb ntawm cov complexes tsim los ntawm HEC / PAA, MC / PAA thiab HPC / PAA yog kwv yees li 2.9, 3.2 thiab 3.7, feem. Qhov tseem ceeb pH ntawm HPC / PAA yog siab dua li ntawm HEC / PAA, uas zoo ib yam nrog LBL membrane.
Kev nqus dej ua haujlwm ntawm CE / PAA membrane:
CES yog nplua nuj nyob rau hauv hydroxyl pawg kom nws muaj dej zoo thiab tuav dej. Siv HEC / PAA daim nyias nyias ua piv txwv, lub peev xwm adsorption ntawm hydrogen-bonded CE / PAA membrane rau dej hauv ib puag ncig tau kawm. Tus cwj pwm los ntawm spectral interferometry, zaj duab xis thickness nce raws li zaj duab xis absorbs dej. Nws tau muab tso rau hauv ib puag ncig nrog kho cov av noo ntawm 25 ° C rau 24 teev kom ua tiav cov dej sib npaug. Cov yeeb yaj kiab tau qhuav hauv qhov cub nqus (40 ° C) rau 24 teev kom tshem tawm cov dej noo tag.
Raws li cov av noo nce, zaj duab xis thickens. Nyob rau hauv qhov chaw tsis muaj av noo ntawm 30% -50%, lub thickness loj hlob kuj qeeb. Thaum cov av noo ntau tshaj 50%, lub thickness loj hlob sai. Piv nrog rau hydrogen-bonded PVPON / PAA daim nyias nyias, HEC / PAA daim nyias nyias tuaj yeem nqus dej ntau los ntawm ib puag ncig. Nyob rau hauv qhov xwm txheej ntawm cov av noo ntawm 70% (25 ° C), qhov thickening ntau ntawm PVPON / PAA zaj duab xis yog li 4%, thaum HEC / PAA zaj duab xis siab txog li 18%. Cov txiaj ntsig tau pom tias txawm hais tias qee qhov OH pawg hauv HEC / PAA system tau koom nrog kev tsim cov ntawv cog lus hydrogen, tseem muaj ntau pawg OH cuam tshuam nrog dej hauv ib puag ncig. Yog li, HEC / PAA system muaj cov dej nqus dej zoo.
nyob rau hauv xaus
(1) HPC / PAA system nrog qhov siab tshaj plaws hydrogen bonding degree ntawm CE thiab PAA muaj kev loj hlob sai tshaj plaws ntawm lawv, MC / PAA nyob rau hauv nruab nrab, thiab HEC / PAA yog qhov qis tshaj.
(2) HEC/PAA zaj duab xis tau qhia txog txoj kev loj hlob ntawm txoj kab thoob plaws hauv cov txheej txheem kev npaj, thaum lwm ob zaj duab xis MC/PAA thiab HPC/PAA tau qhia txog kev loj hlob ntawm thawj ob peb lub voj voog, thiab tom qab ntawd hloov mus rau hauv hom kev loj hlob linear.
(3) Kev loj hlob ntawm CE / PAA zaj duab xis muaj kev vam khom rau cov tshuaj pH. Thaum cov tshuaj pH siab dua nws cov ntsiab lus tseem ceeb, PAA thiab CE tsis tuaj yeem sib sau ua ib zaj duab xis. Kev sib sau ua ke CE / PAA daim nyias nyias yog soluble hauv cov tshuaj pH siab.
(4) Txij li thaum CE / PAA zaj duab xis yog nplua nuj nyob rau hauv OH thiab COOH, kev kho cua sov ua rau nws hla kev sib txuas. Tus ntoo khaub lig-txuas CE / PAA daim nyias nyias muaj kev ruaj ntseg zoo thiab yog insoluble hauv siab pH daws.
(5) CE / PAA zaj duab xis muaj peev xwm adsorption zoo rau cov dej hauv ib puag ncig.
Post lub sij hawm: Feb-18-2023