Isizinda Socwaningo
Njengesisetshenziswa esingokwemvelo, esichichimayo nesivuselelekayo, i-cellulose ihlangabezana nezinselele ezinkulu ekusetshenzisweni okungokoqobo ngenxa yokungancibiliki kwayo nokuncibilika okulinganiselwe.I-crystallinity ephezulu kanye ne-high-density yamabhondi e-hydrogen esakhiweni se-cellulose ayenza ilulazeke kodwa ingancibiliki ngesikhathi senqubo yokubamba, futhi ingancibiliki emanzini nasezincibilikisini eziningi eziphilayo.Okuphuma kuzo kukhiqizwa i-esterification kanye ne-etherification yamaqembu e-hydroxyl kumayunithi we-anhydroglucose ochungechungeni lwe-polymer, futhi izobonisa izici ezithile ezihlukile uma kuqhathaniswa neselulosi yemvelo.Ukusabela kwe-etherification ye-cellulose kungakhiqiza ama-ether amaningi e-cellulose ancibilika emanzini, njenge-methyl cellulose (MC), i-hydroxyethyl cellulose (HEC) ne-hydroxypropyl cellulose (HPC), asetshenziswa kakhulu ekudleni, kwizimonyo, kwezemithi nakwezokwelapha.I-CE encibilikayo emanzini ingakha amapholymer ahlanganiswe ne-hydrogen anama-polycarboxylic acid nama-polyphenols.
I-Layer-by-layer assembly (LBL) iyindlela ephumelelayo yokulungiselela amafilimu amancane ayinhlanganisela ye-polymer.Okulandelayo kuchaza ngokuyinhloko ukuhlanganiswa kwe-LBL kwama-CE amathathu ahlukene e-HEC, MC kanye ne-HPC ne-PAA, kuqhathanise ukuziphatha kwawo komhlangano, futhi kuhlaziya umthelela wababambele ekuhlanganisweni kwe-LBL.Phenya umthelela we-pH ekugqileni kwefilimu, kanye nomehluko ohlukile we-pH ekubunjweni nasekuhlakazweni kwefilimu, futhi uthuthukise izici zokumunca amanzi ze-CE/PAA.
Izinto Zokuhlola:
I-Polyacrylic acid (PAA, Mw = 450,000).I-viscosity ye-2wt.% yesixazululo esinamanzi se-hydroxyethylcellulose (HEC) singama-300 mPa·s, futhi izinga lokushintsha lingu-2.5.I-Methylcellulose (MC, isixazululo se-aqueous esingu-2wt.% esine-viscosity engu-400 mPa·s kanye ne-degree of substitution of 1.8).I-Hydroxypropyl cellulose (HPC, isixazululo samanzi esingu-2wt.% esine-viscosity engu-400 mPa·s kanye nezinga lokushintsha elingu-2.5).
Ukulungiswa kwefilimu:
Ilungiswe ngokuhlanganiswa kongqimba lwekristalu oluwuketshezi ku-silicon ku-25°C.Indlela yokwelapha ye-matrix yesilayidi imi kanje: cwilisa kusisombululo esine-acidic (H2SO4/H2O2, 7/3Vol/VOL) imizuzu engu-30, bese ugeza ngamanzi akhishwe kaningi izikhathi eziningana kuze kube yilapho i-pH ingathathi hlangothi, futhi ekugcineni yome nge-nitrogen ehlanzekile.Ukuhlanganiswa kwe-LBL kwenziwa kusetshenziswa imishini ezenzakalelayo.I-substrate yacwiliswa ngokuhlukile kusixazululo se-CE (0.2 mg/mL) nesisombululo se-PAA (0.2 mg/mL), isisombululo ngasinye sicwiliswe imizuzu emi-4.Ukucwiliswa okuthathu kokugeza okuyiminithi elingu-1 ngakunye emanzini a-deionized kwenziwa phakathi kwesisombululo ngasinye ukuze kukhishwe i-polymer enamathiselwe ngokukhululekile.Amanani e-pH esixazululo somhlangano kanye nesisombululo sokuwasha kokubili kulungiswe ku-pH 2.0.Amafilimu alungisiwe achazwa ngokuthi (CE/PAA)n, lapho u-n ekhomba umjikelezo wokuhlanganisa.(HEC/PAA)40, (MC/PAA)30 kanye (HPC/PAA)30 zilungiswe kakhulukazi.
Ukulingiswa Kwefilimu:
Ukubuka okuseduze kokujwayelekile kwarekhodwa futhi kwahlaziywa nge-NanoCalc-XR Ocean Optics, futhi ubukhulu bamafilimu afakwe ku-silicon balinganiswa.Nge-silicon substrate engenalutho njengengemuva, i-spectrum ye-FT-IR yefilimu elincanyana ku-silicon substrate yaqoqwa ku-Nicolet 8700 infrared spectrometer.
Ukusebenzisana kwebhondi ye-Hydrogen phakathi kwe-PAA nama-CEs:
Ukuhlanganiswa kwe-HEC, MC kanye ne-HPC ne-PAA kumafilimu e-LBL.I-spectra ye-infrared ye-HEC/PAA, MC/PAA ne-HPC/PAA ikhonjisiwe emfanekisweni.Amasiginali we-IR aqinile we-PAA ne-CES angabonwa ngokucacile ku-spectra ye-IR ye-HEC/PAA, MC/PAA ne-HPC/PAA.I-spectroscopy ye-FT-IR ingahlaziya ukuhlangana kwebhondi ye-hydrogen phakathi kwe-PAA ne-CES ngokuqapha ukushintsha kwamabhendi okumunca okuyisici.Ukuhlangana kwe-hydrogen phakathi kwe-CES ne-PAA kwenzeka ikakhulukazi phakathi kwe-hydroxyl oxygen ye-CES neqembu le-COOH le-PAA.Ngemva kokwakhiwa kwebhondi ye-hydrogen, isiqongo esinwebekayo esibomvu sishintshela kusiqondiso semvamisa ephansi.
Inani eliphakeme le-1710 cm-1 labonwa nge-PAA powder ehlanzekile.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 nempushana ye-PAA emsulwa, ubude bamafilimu e-HPC/PAA, MC/PAA kanye ne-HEC/PAA bugudluzwe ngo-14, 10 no-8 cm−1, ngokulandelana.Ibhondi ye-hydrogen phakathi kwe-ether oxygen ne-COOH iphazamisa isibopho se-hydrogen phakathi kwamaqembu e-COOH.Uma amabhondi e-hydrogen engeziwe akheka phakathi kwe-PAA ne-CE, kukhulu ukushintshwa okuphezulu kwe-CE/PAA ku-IR spectra.I-HPC inezinga eliphezulu kakhulu le-hydrogen bond complexation, i-PAA ne-MC iphakathi nendawo, futhi i-HEC iphansi kakhulu.
Ukukhula kokuziphatha kwamafilimu ayinhlanganisela ye-PAA nama-CEs:
Ukuziphatha kokwenza ifilimu kwe-PAA nama-CEs ngesikhathi sokuhlanganiswa kwe-LBL kwaphenywa kusetshenziswa i-QCM kanye ne-spectral interferometry.I-QCM iyasebenza ekuqapheni ukukhula kwefilimu ku-situ phakathi nemijikelezo embalwa yokuqala yomhlangano.Ama-interferometer e-Spectral afanele amafilimu akhule ngaphezu kwemijikelezo eyi-10.
Ifilimu ye-HEC/PAA ibonise ukukhula okuqondile kuyo yonke inqubo yokuhlanganisa ye-LBL, kuyilapho amafilimu e-MC/PAA kanye ne-HPC/PAA abonisa ukukhula okuphawulekayo ezigabeni zokuqala zokuhlanganisa abese eguqulwa abe ukukhula okulandelanayo.Esifundeni sokukhula esilandelanayo, izinga eliphezulu lokuyinkimbinkimbi, kukhulu ukukhula kogqinsi ngomjikelezo womhlangano ngamunye.
Umphumela wesisombululo pH ekukhuleni kwefilimu:
Inani le-pH lesixazululo lithinta ukukhula kwefilimu eyinhlanganisela ye-polymer eboshelwe nge-hydrogen.Njenge-polyelectrolyte ebuthakathaka, i-PAA izofakwa i-ionized futhi ikhokhiswe kabi njengoba i-pH yesisombululo ikhula, ngaleyo ndlela ivimbele inhlangano ye-hydrogen bond.Lapho idigri ye-ionization ye-PAA ifinyelela izinga elithile, i-PAA ayikwazanga ukuhlangana ibe yifilimu enabamukeli bebhondi ye-hydrogen ku-LBL.
Ugqinsi lwefilimu lwehla ngokunyuka kwesixazululo se-pH, futhi ukujiya kwefilimu kwehle kungazelelwe ku-pH2.5 HPC/PAA kanye ne-pH3.0-3.5 HPC/PAA.Iphuzu elibalulekile le-HPC/PAA licishe libe ngu-pH 3.5, kuyilapho lelo le-HEC/PAA licishe libe ngu-3.0.Lokhu kusho ukuthi uma i-pH yesisombululo somhlangano ingaphezulu kuka-3.5, ifilimu ye-HPC/PAA ayikwazi ukwakhiwa, futhi lapho i-pH yesisombululo ingaphezu kuka-3.0, ifilimu ye-HEC/PAA ayikwazi ukwakhiwa.Ngenxa yezinga eliphakeme le-hydrogen bond complexation ye-HPC/PAA ulwelwesi, inani le-pH elibalulekile le-HPC/PAA ulwelwesi liphezulu kunalelo le-HEC/PAA membrane.Esixazululweni esingenawo usawoti, amanani e-pH abalulekile ezinkimbinkimbi ezakhiwe yi-HEC/PAA, MC/PAA ne-HPC/PAA ayecishe abe ngu-2.9, 3.2 no-3.7, ngokulandelana.I-pH ebucayi ye-HPC/PAA iphezulu kunaleyo ye-HEC/PAA, ehambisana naleyo yolwelwesi lwe-LBL.
Ukusebenza kokumuncwa kwamanzi kwe-CE/PAA membrane:
I-CES inothile ngamaqembu e-hydroxyl ukuze ibe nokumunca kahle kwamanzi kanye nokugcinwa kwamanzi.Kuthathwa ulwelwesi lwe-HEC/PAA njengesibonelo, umthamo wokukhangisa we-hydrogen-bonded CE/PAA membrane emanzini emvelweni wacwaningwa.Ebonakala nge-spectral interferometry, ubukhulu befilimu buyanda njengoba ifilimu imunca amanzi.Ibekwe endaweni enomswakama olungisekayo ku-25°C amahora angu-24 ukuze kuzuzwe ukulingana kokumuncwa kwamanzi.Amafilimu omiswa kuhhavini wevacuum (40 ° C) amahora angama-24 ukuze asuse ngokuphelele umswakama.
Njengoba umswakama ukhula, ifilimu iyaqina.Endaweni enomswakama ophansi ka-30% -50%, ukukhula kogqinsi kuhamba kancane.Uma umswakama udlula ama-50%, ukujiya kukhula ngokushesha.Uma kuqhathaniswa ne-hydrogen-bonded PVPON/PAA membrane, ulwelwesi lwe-HEC/PAA lungakwazi ukumunca amanzi amaningi endaweni ezungezile.Ngaphansi kwesimo somswakama ohlobene ongu-70% (25°C), ububanzi bokujiya befilimu ye-PVPON/PAA bucishe bube ngu-4%, kuyilapho lefilimu ye-HEC/PAA iphezulu cishe cishe ngo-18%.Imiphumela yabonisa ukuthi nakuba inani elithile lamaqembu e-OH ohlelweni lwe-HEC/PAA libambe iqhaza ekwakhiweni kwamabhondi e-hydrogen, kwakusenenani elikhulu lamaqembu e-OH asebenzisana namanzi emvelweni.Ngakho-ke, uhlelo lwe-HEC/PAA lunezinto ezinhle zokumunca amanzi.
Ekuphetheni
(1) Uhlelo lwe-HPC/PAA olunezinga eliphezulu kakhulu le-hydrogen bonding le-CE ne-PAA linokukhula okusheshayo phakathi kwazo, i-MC/PAA iphakathi nendawo, futhi i-HEC/PAA iphansi kakhulu.
(2) Ifilimu ye-HEC/PAA ibonise imodi yokukhula eqondile kuyo yonke inqubo yokulungiselela, kuyilapho amanye amafilimu amabili i-MC/PAA ne-HPC/PAA abonisa ukukhula okuphawulekayo emijikelezweni embalwa yokuqala, abese eguqulwa abe imodi yokukhula elandelanayo.
(3) Ukukhula kwefilimu ye-CE/PAA kuncike kakhulu esixazululweni se-pH.Lapho isisombululo se-pH siphezulu kunephuzu laso elibucayi, i-PAA ne-CE azikwazi ukuhlangana zibe ifilimu.I-membrane ye-CE/PAA ehlanganisiwe yayincibilika kuzixazululo ze-pH ephezulu.
(4) Njengoba ifilimu ye-CE/PAA inothe nge-OH ne-COOH, ukwelashwa kokushisa kuyenza ixhumeke.I-membrane ye-CE/PAA exhunywe ngokuphambano inokuqina okuhle futhi ayincibiliki ezixazululweni ze-pH ephezulu.
(5) Ifilimu ye-CE/PAA inamandla okukhangisa amanzi endaweni ezungezile.
Isikhathi sokuthumela: Feb-18-2023