Keeb Kwm Kev Tshawb Fawb
Raws li ib qho khoom siv ntuj, muaj ntau thiab rov ua dua tshiab, cellulose ntsib teeb meem loj hauv kev siv ua haujlwm vim nws cov khoom tsis yaj thiab cov khoom solubility tsawg. Lub crystallinity siab thiab cov hydrogen bonds siab hauv cov qauv cellulose ua rau nws lwj tab sis tsis yaj thaum lub sijhawm muaj, thiab tsis yaj hauv dej thiab feem ntau cov kuab tshuaj organic. Lawv cov derivatives yog tsim los ntawm esterification thiab etherification ntawm cov hydroxyl pawg ntawm cov anhydroglucose units hauv cov saw polymer, thiab yuav ua rau pom qee yam khoom sib txawv piv rau cov cellulose ntuj. Cov tshuaj etherification ntawm cellulose tuaj yeem tsim ntau cov dej-soluble cellulose ethers, xws li methyl cellulose (MC), hydroxyethyl cellulose (HEC) thiab hydroxypropyl cellulose (HPC), uas yog siv dav hauv cov khoom noj, tshuaj pleev ib ce, hauv tshuaj thiab tshuaj. Cov dej-soluble CE tuaj yeem tsim cov hydrogen-bonded polymers nrog polycarboxylic acids thiab polyphenols.
Kev sib dhos ua ke ntawm cov txheej (LBL) yog ib txoj hauv kev zoo rau kev npaj cov zaj duab xis nyias nyias polymer. Cov hauv qab no feem ntau piav qhia txog kev sib dhos LBL ntawm peb qhov sib txawv CEs ntawm HEC, MC thiab HPC nrog PAA, piv rau lawv tus cwj pwm sib dhos, thiab tshuaj xyuas qhov cuam tshuam ntawm cov khoom hloov pauv rau kev sib dhos LBL. Tshawb xyuas qhov cuam tshuam ntawm pH rau qhov tuab ntawm zaj duab xis, thiab qhov sib txawv ntawm pH rau kev tsim zaj duab xis thiab kev yaj, thiab txhim kho cov khoom nqus dej ntawm CE/PAA.
Cov Khoom Siv Sim:
Polyacrylic acid (PAA, Mw = 450,000). Qhov viscosity ntawm 2wt.% aqueous kua ntawm hydroxyethylcellulose (HEC) yog 300 mPa·s, thiab qib ntawm kev hloov pauv yog 2.5. Methylcellulose (MC, 2wt.% aqueous kua nrog viscosity ntawm 400 mPa·s thiab qib ntawm kev hloov pauv ntawm 1.8). Hydroxypropyl cellulose (HPC, 2wt.% aqueous kua nrog viscosity ntawm 400 mPa·s thiab qib ntawm kev hloov pauv ntawm 2.5).
Kev npaj zaj duab xis:
Npaj los ntawm cov kua siv lead ua ke ntawm silicon ntawm 25°C. Txoj kev kho ntawm cov slide matrix yog raws li nram no: tsau hauv cov kua qaub (H2SO4/H2O2, 7/3Vol/VOL) rau 30 feeb, tom qab ntawd yaug nrog dej deionized ntau zaus kom txog thaum pH dhau los ua qhov nruab nrab, thiab thaum kawg qhuav nrog nitrogen ntshiab. LBL sib dhos ua tiav siv tshuab tsis siv neeg. Lub substrate tau ntub dej hauv CE kua (0.2 mg/mL) thiab PAA kua (0.2 mg/mL), txhua cov kua tau ntub dej rau 4 feeb. Peb zaug yaug dej ntawm 1 feeb txhua qhov hauv dej deionized tau ua ntawm txhua qhov kev ntxuav dej kom tshem tawm cov polymer uas tsis sib txuas. Cov nqi pH ntawm cov kua sib dhos thiab cov kua yaug tau kho rau pH 2.0. Cov yeeb yaj kiab uas tau npaj tseg tau cim ua (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.
Kev piav qhia txog zaj duab xis:
Cov spectra reflectance ze li qub tau raug kaw thiab tshuaj xyuas nrog NanoCalc-XR Ocean Optics, thiab qhov tuab ntawm cov zaj duab xis uas tso rau ntawm silicon tau raug ntsuas. Nrog lub silicon substrate dawb paug ua keeb kwm yav dhau, FT-IR spectrum ntawm cov zaj duab xis nyias nyias ntawm lub silicon substrate tau raug sau rau ntawm Nicolet 8700 infrared spectrometer.
Kev sib cuam tshuam ntawm hydrogen bond ntawm PAA thiab CEs:
Kev sib dhos ntawm HEC, MC thiab HPC nrog PAA rau hauv LBL zaj duab xis. Cov duab infrared ntawm HEC/PAA, MC/PAA thiab HPC/PAA tau qhia nyob rau hauv daim duab. Cov teeb liab IR muaj zog ntawm PAA thiab CES tuaj yeem pom tseeb hauv IR spectra ntawm HEC/PAA, MC/PAA thiab HPC/PAA. FT-IR spectroscopy tuaj yeem tshuaj xyuas qhov sib txuas hydrogen ntawm PAA thiab CES los ntawm kev saib xyuas qhov hloov pauv ntawm cov kab nqus dej. Qhov sib txuas hydrogen ntawm CES thiab PAA feem ntau tshwm sim ntawm hydroxyl oxygen ntawm CES thiab COOH pawg ntawm PAA. Tom qab hydrogen sib txuas tau tsim, qhov ncab peak liab hloov mus rau qhov kev taw qhia zaus qis.
Muaj qhov siab tshaj plaws 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 CEs sib txawv, cov siab tshaj plaws ntawm HEC/PAA, MC/PAA thiab MPC/PAA zaj duab xis tau nyob ntawm 1718 cm-1, 1720 cm-1 thiab 1724 cm-1, raws li. Piv nrog cov hmoov PAA ntshiab, qhov ntev siab tshaj plaws ntawm HPC/PAA, MC/PAA thiab HEC/PAA zaj duab xis hloov pauv los ntawm 14, 10 thiab 8 cm−1, raws li. Cov hydrogen bond ntawm ether oxygen thiab COOH cuam tshuam cov hydrogen bond ntawm COOH pawg. Cov hydrogen bonds ntau dua tsim ntawm PAA thiab CE, qhov siab tshaj plaws ntawm CE/PAA hloov pauv hauv IR spectra. HPC muaj qib siab tshaj plaws ntawm hydrogen bond complexation, PAA thiab MC nyob hauv nruab nrab, thiab HEC yog qhov qis tshaj plaws.
Kev loj hlob ntawm cov yeeb yaj kiab sib xyaw ntawm PAA thiab CEs:
Tus cwj pwm tsim zaj duab xis ntawm PAA thiab CEs thaum lub sijhawm sib dhos LBL tau tshawb xyuas siv QCM thiab spectral interferometry. QCM muaj txiaj ntsig zoo rau kev saib xyuas kev loj hlob ntawm zaj duab xis hauv qhov chaw thaum lub sijhawm thawj ob peb lub voj voog sib dhos. Spectral interferometers yog qhov tsim nyog rau cov zaj duab xis uas loj hlob tshaj 10 lub voj voog.
Cov yeeb yaj kiab HEC/PAA tau qhia txog kev loj hlob linear thoob plaws hauv LBL cov txheej txheem sib dhos, thaum cov yeeb yaj kiab MC/PAA thiab HPC/PAA tau qhia txog kev loj hlob exponential hauv theem thaum ntxov ntawm kev sib dhos thiab tom qab ntawd hloov mus ua kev loj hlob linear. Hauv thaj chaw loj hlob linear, qhov siab dua ntawm kev sib xyaw ua ke, qhov loj dua ntawm qhov tuab ib lub voj voog sib dhos.
Cov nyhuv ntawm cov kua pH rau kev loj hlob ntawm zaj duab xis:
Tus nqi pH ntawm cov tshuaj cuam tshuam rau kev loj hlob ntawm cov zaj duab xis polymer sib xyaw hydrogen bonded. Raws li cov polyelectrolyte tsis muaj zog, PAA yuav raug ionized thiab them tsis zoo thaum pH ntawm cov tshuaj nce ntxiv, yog li ntawd inhibition hydrogen bond association. Thaum qib ntawm ionization ntawm PAA mus txog qee qib, PAA tsis tuaj yeem sib sau ua ke rau hauv zaj duab xis nrog cov hydrogen bond acceptors hauv LBL.
Qhov tuab ntawm zaj duab xis txo qis nrog rau qhov nce ntawm pH ntawm cov kua, thiab qhov tuab ntawm zaj duab xis txo qis sai sai ntawm pH2.5 HPC/PAA thiab pH3.0-3.5 HPC/PAA. Lub ntsiab lus tseem ceeb ntawm HPC/PAA yog li pH 3.5, thaum HEC/PAA yog li 3.0. Qhov no txhais tau tias thaum pH ntawm cov kua sib dhos siab dua 3.5, zaj duab xis HPC/PAA tsis tuaj yeem tsim tau, thiab thaum pH ntawm cov kua siab dua 3.0, zaj duab xis HEC/PAA tsis tuaj yeem tsim tau. Vim yog qib siab ntawm hydrogen bond complexation ntawm HPC/PAA membrane, qhov tseem ceeb pH ntawm HPC/PAA membrane siab dua li ntawm HEC/PAA membrane. Hauv cov kua tsis muaj ntsev, qhov tseem ceeb pH ntawm cov complexes tsim los ntawm HEC/PAA, MC/PAA thiab HPC/PAA yog li 2.9, 3.2 thiab 3.7, raws li. Qhov pH tseem ceeb ntawm HPC/PAA siab dua li ntawm HEC/PAA, uas yog sib xws nrog ntawm LBL membrane.
Kev ua tau zoo ntawm kev nqus dej ntawm CE / PAA membrane:
CES muaj ntau pawg hydroxyl kom nws nqus tau dej zoo thiab khaws dej tau zoo. Piv txwv li, siv HEC/PAA membrane ua piv txwv, lub peev xwm nqus tau ntawm hydrogen-bonded CE/PAA membrane rau dej hauv ib puag ncig tau kawm. Ua raws li spectral interferometry, zaj duab xis tuab nce ntxiv thaum zaj duab xis nqus dej. Nws tau muab tso rau hauv ib puag ncig nrog qhov av noo hloov kho tau ntawm 25°C rau 24 teev kom ua tiav qhov sib npaug ntawm kev nqus dej. Cov zaj duab xis tau ziab hauv lub qhov cub nqus tsev (40°C) rau 24 teev kom tshem tawm cov av noo tag nrho.
Thaum cov av noo nce ntxiv, zaj duab xis yuav tuab zuj zus. Hauv thaj chaw uas muaj av noo tsawg ntawm 30% -50%, qhov tuab zuj zus qeeb heev. Thaum cov av noo tshaj 50%, qhov tuab zuj zus sai. Piv nrog rau daim nyias nyias PVPON/PAA uas muaj hydrogen sib txuas, daim nyias nyias HEC/PAA tuaj yeem nqus dej ntau dua los ntawm ib puag ncig. Hauv qab qhov av noo ntawm 70% (25°C), qhov tuab ntawm zaj duab xis PVPON/PAA yog li 4%, thaum zaj duab xis HEC/PAA siab txog li 18%. Cov txiaj ntsig qhia tau tias txawm hais tias muaj qee pawg OH hauv HEC/PAA system koom nrog kev tsim cov hydrogen bonds, tseem muaj ntau pawg OH sib cuam tshuam nrog dej hauv ib puag ncig. Yog li ntawd, HEC/PAA system muaj cov yam ntxwv nqus dej zoo.
xaus lus
(1) Lub kaw lus HPC/PAA uas muaj qib hydrogen bonding siab tshaj plaws ntawm CE thiab PAA muaj kev loj hlob sai tshaj plaws ntawm lawv, MC/PAA nyob hauv nruab nrab, thiab HEC/PAA qis tshaj plaws.
(2) Zaj duab xis HEC/PAA tau qhia txog hom kev loj hlob linear thoob plaws hauv cov txheej txheem npaj, thaum ob zaj duab xis MC/PAA thiab HPC/PAA tau qhia txog kev loj hlob exponential hauv ob peb lub voj voog thawj zaug, thiab tom qab ntawd hloov mus rau hauv hom kev loj hlob linear.
(3) Kev loj hlob ntawm zaj duab xis CE/PAA muaj kev vam khom rau pH ntawm cov tshuaj. Thaum pH ntawm cov tshuaj siab dua nws qhov tseem ceeb, PAA thiab CE tsis tuaj yeem sib sau ua ke rau hauv zaj duab xis. Daim nyias nyias CE/PAA uas tau sib sau ua ke tau yaj hauv cov tshuaj pH siab.
(4) Vim tias zaj duab xis CE/PAA muaj ntau OH thiab COOH, kev kho cua sov ua rau nws sib txuas. Daim nyias nyias CE/PAA sib txuas muaj kev ruaj khov zoo thiab tsis yaj hauv cov kua pH siab.
(5) Zaj duab xis CE/PAA muaj peev xwm nqus dej tau zoo hauv ib puag ncig.
Lub sijhawm tshaj tawm: Lub Ob Hlis-18-2023