Isizinda Socwaningo
Njengomthombo wemvelo, omningi futhi ovuselelekayo, i-cellulose ihlangabezana nezinselele ezinkulu ekusetshenzisweni okusebenzayo ngenxa yezakhiwo zayo ezingancibiliki kanye nokuncibilika okulinganiselwe. Ukuqina okuphezulu kwe-crystallinity kanye nezibopho ze-hydrogen eziphezulu esakhiweni se-cellulose kwenza ukuthi yonakale kodwa ingancibiliki ngesikhathi senqubo yokubamba, futhi ingancibiliki emanzini nasezithambisweni eziningi eziphilayo. Ama-derivatives azo akhiqizwa yi-esterification kanye ne-etherification yamaqembu e-hydroxyl kumayunithi e-anhydroglucose ku-polymer chain, futhi azobonisa ezinye izakhiwo ezihlukile uma kuqhathaniswa ne-cellulose yemvelo. Ukusabela kwe-etherification kwe-cellulose kungakhiqiza ama-ether amaningi e-cellulose ancibilika emanzini, njenge-methyl cellulose (MC), i-hydroxyethyl cellulose (HEC) kanye ne-hydroxypropyl cellulose (HPC), asetshenziswa kabanzi ekudleni, ezimonyweni, kwezemithi nakwezokwelapha. I-CE encibilika emanzini ingakha ama-polymer ahlanganiswe ne-hydrogen ane-polycarboxylic acid kanye nama-polyphenols.
Ukuhlanganiswa kwe-Layer-by-layer (LBL) kuyindlela ephumelelayo yokulungiselela amafilimu amancane ahlanganisiwe e-polymer. Okulandelayo kuchaza kakhulu ukuhlanganiswa kwe-LBL kwama-CE amathathu ahlukene e-HEC, MC kanye ne-HPC ne-PAA, kuqhathanisa ukuziphatha kwawo kokuhlanganiswa, futhi kuhlaziye ithonya lezinto ezithatha indawo ekuhlanganisweni kwe-LBL. Phenya umphumela we-pH ekujikeni kwefilimu, kanye nomehluko ohlukile we-pH ekwakhekeni nasekuncibilikeni kwefilimu, bese uthuthukisa izakhiwo zokumunca amanzi ze-CE/PAA.
Izinto Zokuhlola:
I-Polyacrylic acid (PAA, Mw = 450,000). I-viscosity yesisombululo samanzi esingu-2wt.% se-hydroxyethylcellulose (HEC) ingu-300 mPa·s, kanti izinga lokushintsha lingu-2.5. I-Methylcellulose (MC, isixazululo samanzi esingu-2wt.% esine-viscosity engu-400 mPa·s kanye nezinga lokushintsha elingu-1.8). I-Hydroxypropyl cellulose (HPC, isixazululo samanzi esingu-2wt.% esine-viscosity engu-400 mPa·s kanye nezinga lokushintsha elingu-2.5).
Ukulungiselela ifilimu:
Kulungiselelwe ngenhlanganisela yengqimba yekristalu eliwuketshezi ku-silicon ku-25°C. Indlela yokwelapha ye-slide matrix yilena elandelayo: cwilisa kwisisombululo esinobuthi (H2SO4/H2O2, 7/3Vol/VOL) imizuzu engama-30, bese ugeza ngamanzi acwebezelwe izikhathi eziningana kuze kube yilapho i-pH iba ngathathi hlangothi, bese ekugcineni yomisa nge-nitrogen emsulwa. Ukuhlanganiswa kwe-LBL kwenziwa kusetshenziswa imishini ezenzakalelayo. I-substrate yacwiliswa ngokushintshana kwisisombululo se-CE (0.2 mg/mL) kanye nesisombululo se-PAA (0.2 mg/mL), isixazululo ngasinye sacwiliswa imizuzu emi-4. Ukuhlanza kathathu komzuzu owodwa ngakunye emanzini acwebezelwe kwenziwa phakathi kokucwilisa kwesisombululo ngasinye ukuze kususwe i-polymer enamathele kancane. Amanani e-pH esisombululo senhlangano kanye nesisombululo sokuhlanza womabili alungiswe ku-pH 2.0. Amafilimu alungisiwe abizwa ngokuthi (CE/PAA)n, lapho u-n esho umjikelezo wenhlangano. (HEC/PAA)40, (MC/PAA)30 kanye (HPC/PAA)30 alungiselelwe kakhulu.
Ukuchazwa kwefilimu:
Ama-spectra okukhanya acishe abe ajwayelekile aqoshwa futhi ahlaziywa nge-NanoCalc-XR Ocean Optics, futhi ubukhulu bamafilimu afakwe ku-silicon balinganiswa. Nge-substrate ye-silicon engenalutho njengesizinda, i-spectrum ye-FT-IR yefilimu encane ku-substrate ye-silicon yaqoqwa ku-spectrometer ye-infrared ye-Nicolet 8700.
Ukusebenzisana kwe-hydrogen bond phakathi kwe-PAA kanye ne-CE:
Ukuhlanganiswa kwe-HEC, MC kanye ne-HPC ne-PAA kumafilimu e-LBL. Ama-spectra e-infrared e-HEC/PAA, MC/PAA kanye ne-HPC/PAA aboniswe esithombeni. Izimpawu ze-IR ezinamandla ze-PAA kanye ne-CES zingabonakala ngokucacile kuma-spectra e-IR e-HEC/PAA, MC/PAA kanye ne-HPC/PAA. I-spectroscopy ye-FT-IR ingahlaziya ukuhlanganiswa kwesibopho se-hydrogen phakathi kwe-PAA kanye ne-CES ngokuqapha ukushintsha kwamabhande okumunca ahlukile. Ukuhlanganiswa kwe-hydrogen phakathi kwe-CES kanye ne-PAA kwenzeka kakhulu phakathi kwe-hydroxyl oxygen ye-CES kanye neqembu le-COOH le-PAA. Ngemva kokwakheka kwesibopho se-hydrogen, ubomvu obunwebekayo bushintshela esiqondisweni semvamisa ephansi.
Kwabonakala ukuphakama okungu-1710 cm-1 kwempuphu ye-PAA emsulwa. Lapho i-polyacrylamide ihlanganiswa ibe amafilimu anama-CE ahlukene, iziqongo zamafilimu e-HEC/PAA, MC/PAA kanye ne-MPC/PAA zazitholakala ku-1718 cm-1, 1720 cm-1 kanye no-1724 cm-1, ngokulandelana. Uma kuqhathaniswa nempuphu ye-PAA emsulwa, ubude beziqongo zamafilimu e-HPC/PAA, MC/PAA kanye ne-HEC/PAA bushintshwe ngo-14, 10 kanye no-8 cm−1, ngokulandelana. Isibopho se-hydrogen phakathi kwe-ether oxygen kanye ne-COOH siphazamisa isibopho se-hydrogen phakathi kwamaqembu e-COOH. Uma kwakheka izibopho ze-hydrogen eziningi phakathi kwe-PAA kanye ne-CE, kulapho kukhula khona ukushintsha kweziqongo kwe-CE/PAA kuma-spectra e-IR. I-HPC inezinga eliphakeme kakhulu lokuhlanganiswa kwezibopho ze-hydrogen, i-PAA kanye ne-MC ziphakathi nendawo, kanti i-HEC iyona ephansi kakhulu.
Ukuziphatha kokukhula kwamafilimu ahlanganisiwe e-PAA nama-CE:
Ukuziphatha kokwakha ifilimu kwe-PAA kanye ne-CE ngesikhathi sokuhlanganiswa kwe-LBL kuhlolwe kusetshenziswa i-QCM kanye ne-spectral interferometry. I-QCM iyasebenza ekuqapheni ukukhula kwefilimu endaweni ngesikhathi sokujikeleza kokuqala kokuhlanganiswa. Ama-spectral interferometer afaneleka kumafilimu akhuliswe ngaphezu kwemijikelezo eyi-10.
Ifilimu ye-HEC/PAA ibonise ukukhula okuqondile kuyo yonke inqubo yokuhlanganisa i-LBL, kuyilapho amafilimu e-MC/PAA kanye ne-HPC/PAA abonise ukukhula okubonakalayo ezigabeni zokuqala zokuhlanganisa abese eguqulwa abe ukukhula okuqondile. Esifundeni sokukhula okuqondile, lapho izinga lobunzima liphakama, kulapho ukukhula kobukhulu kukhulu khona ngomjikelezo ngamunye wokuhlanganisa.
Umphumela wesisombululo se-pH ekukhuleni kwefilimu:
Inani le-pH lesisombululo lithinta ukukhula kwefilimu ehlanganisiwe ye-polymer eboshwe yi-hydrogen. Njenge-polyelectrolyte ebuthakathaka, i-PAA izofakwa i-ionized futhi ishajwe kabi njengoba i-pH yesisombululo ikhuphuka, ngaleyo ndlela ivimbele ukuhlangana kwe-hydrogen bond. Lapho izinga le-ionization ye-PAA lifinyelela ezingeni elithile, i-PAA ayikwazanga ukuhlangana ibe ifilimu enezamukeli ze-hydrogen bond ku-LBL.
Ubukhulu befilimu behle ngokwanda kwe-pH yesisombululo, kanti ubukhulu befilimu behle ngokuzumayo ku-pH2.5 HPC/PAA kanye ne-pH3.0-3.5 HPC/PAA. Iphuzu elibalulekile le-HPC/PAA licishe libe yi-pH 3.5, kanti ele-HEC/PAA licishe libe yi-3.0. Lokhu kusho ukuthi lapho i-pH yesisombululo sokuhlangana iphakeme kune-3.5, ifilimu ye-HPC/PAA ayikwazi ukwakheka, futhi lapho i-pH yesisombululo iphakeme kune-3.0, ifilimu ye-HEC/PAA ayikwazi ukwakheka. Ngenxa yezinga eliphakeme lokuhlanganiswa kwe-hydrogen bond ye-membrane ye-HPC/PAA, inani le-pH elibalulekile le-membrane ye-HPC/PAA liphakeme kunele-membrane ye-HEC/PAA. Esixazululweni esingenasawoti, amanani e-pH abalulekile e-complexes akhiwe yi-HEC/PAA, i-MC/PAA kanye ne-HPC/PAA ayengaba ngu-2.9, 3.2 kanye no-3.7, ngokulandelana. I-pH ebalulekile ye-HPC/PAA iphakeme kuneye-HEC/PAA, okuhambisana neye-LBL membrane.
Ukusebenza kokumuncwa kwamanzi kwe-CE/PAA membrane:
I-CES icebile ngamaqembu e-hydroxyl ukuze ibe nokumuncwa kwamanzi okuhle kanye nokugcinwa kwamanzi. Uma sibheka i-membrane ye-HEC/PAA njengesibonelo, ikhono lokumuncwa kwe-membrane ye-CE/PAA ene-hydrogen eboshiwe emanzini endaweni ezungezile lafundwa. Njengoba ichazwa yi-spectral interferometry, ukujiya kwefilimu kuyanda njengoba ifilimu imunca amanzi. Yabekwa endaweni enomswakama olungisekayo ku-25°C amahora angama-24 ukuze kufezwe ukulingana kokumuncwa kwamanzi. Amafilimu omiswa kuhhavini we-vacuum (40°C) amahora angama-24 ukuze kususwe ngokuphelele umswakama.
Njengoba umswakama ukhula, ifilimu iyaqina. Endaweni enomswakama ophansi ongu-30%-50%, ukukhula kobukhulu kuhamba kancane. Uma umswakama udlula u-50%, ubukhulu bukhula ngokushesha. Uma kuqhathaniswa nolwelwesi lwe-PVPON/PAA oluboshwe yi-hydrogen, ulwelwesi lwe-HEC/PAA lungamunca amanzi amaningi endaweni ezungezile. Ngaphansi kwesimo somswakama ohlobene ongu-70% (25°C), ububanzi bokuqina kwefilimu ye-PVPON/PAA bungaba ngu-4%, kanti olwefilimu ye-HEC/PAA luphakeme cishe ngo-18%. Imiphumela ibonise ukuthi yize inani elithile lamaqembu e-OH ohlelweni lwe-HEC/PAA lahlanganyela ekwakhiweni kwezibopho ze-hydrogen, kwakusekhona inani elikhulu lamaqembu e-OH asebenzisana namanzi endaweni ezungezile. Ngakho-ke, uhlelo lwe-HEC/PAA lunezakhiwo ezinhle zokumunca amanzi.
Ekuphetheni
(1) Uhlelo lwe-HPC/PAA olunezinga eliphezulu kakhulu lokubopha i-hydrogen le-CE ne-PAA lukhula ngokushesha kakhulu phakathi kwazo, i-MC/PAA iphakathi nendawo, kanti i-HEC/PAA iphansi kakhulu.
(2) Ifilimu ye-HEC/PAA ibonise imodi yokukhula eqondile kuyo yonke inqubo yokulungiselela, kanti amanye amafilimu amabili i-MC/PAA kanye ne-HPC/PAA abonise ukukhula okubonakalayo emijikelezweni embalwa yokuqala, bese eguqulwa abe imodi yokukhula eqondile.
(3) Ukukhula kwefilimu ye-CE/PAA kuncike kakhulu ku-pH yesisombululo. Uma i-pH yesisombululo iphakeme kunephuzu layo elibalulekile, i-PAA ne-CE azikwazi ukuhlangana zibe ifilimu. Ulwelwesi lwe-CE/PAA oluhlanganisiwe lwaluncibilika ezixazululweni ze-pH ephezulu.
(4) Njengoba ifilimu ye-CE/PAA icebile nge-OH kanye ne-COOH, ukwelashwa kokushisa kuyenza ixhumeke. I-membrane ye-CE/PAA exhumeke nge-cross-linked inokuqina okuhle futhi ayincibiliki ezixazululweni ze-pH ephezulu.
(5) Ifilimu ye-CE/PAA inamandla amahle okumunca amanzi endaweni ezungezile.
Isikhathi sokuthunyelwe: Feb-18-2023