Bayanin Bincike
A matsayinta na halitta, mai yalwa kuma mai sabuntawa, cellulose tana fuskantar manyan ƙalubale a aikace-aikace na zahiri saboda rashin narkewarta da ƙarancin halayen narkewarta. Babban haɗin kristal da babban yawan hydrogen a cikin tsarin cellulose yana sa ta lalace amma ba ta narkewa yayin aikin mallaka ba, kuma ba ta narkewa a cikin ruwa da yawancin abubuwan narkewar halitta. Ana samar da abubuwan da aka samo daga gare su ta hanyar esterification da etherification na ƙungiyoyin hydroxyl akan raka'o'in anhydroglucose a cikin sarkar polymer, kuma za su nuna wasu halaye daban-daban idan aka kwatanta da cellulose na halitta. Haɗarin etherification na cellulose na iya samar da ethers cellulose masu narkewa da ruwa da yawa, kamar methyl cellulose (MC), hydroxyethyl cellulose (HEC) da hydroxypropyl cellulose (HPC), waɗanda ake amfani da su sosai a abinci, kayan kwalliya, a cikin magunguna da magunguna. CE mai narkewa da ruwa na iya samar da polymers masu haɗin hydrogen tare da polycarboxylic acid da polyphenols.
Haɗa Layer-by-layer (LBL) hanya ce mai inganci don shirya fina-finan siraran polymer composite. Waɗannan sun fi bayyana haɗa LBL na CEs guda uku daban-daban na HEC, MC da HPC tare da PAA, suna kwatanta halayen haɗarsu, kuma suna nazarin tasirin abubuwan maye akan haɗuwar LBL. Bincika tasirin pH akan kauri fim, da bambance-bambancen pH daban-daban akan samuwar fim da narkewa, da haɓaka halayen sha ruwa na CE/PAA.
Kayan Gwaji:
Polyacrylic acid (PAA, Mw = 450,000). Dankowar ruwan hydroxyethylcellulose (HEC) mai kashi 2wt.% shine 300 mPa·s, kuma matakin maye gurbin shine 2.5. Methylcellulose (MC, ruwan 2wt.% mai dankowa shine 400 mPa·s da kuma matakin maye gurbin 1.8). Hydroxypropyl cellulose (HPC, ruwan 2wt.% mai dankowa shine 400 mPa·s da kuma matakin maye gurbin 2.5).
Shirye-shiryen fim:
An shirya shi ta hanyar haɗakar layukan lu'ulu'u na ruwa a kan silicon a zafin jiki na 25°C. Hanyar maganin matrix ɗin zamiya ita ce kamar haka: jiƙa a cikin ruwan acidic (H2SO4/H2O2, 7/3Vol/VOL) na tsawon minti 30, sannan a wanke da ruwan deionized sau da yawa har sai pH ya zama tsaka tsaki, sannan a ƙarshe a bushe da sinadarin nitrogen mai tsabta. Ana yin haɗakar LBL ta amfani da injina ta atomatik. An jiƙa substrate ɗin a cikin ruwan CE (0.2 mg/mL) da ruwan PAA (0.2 mg/mL), an jiƙa kowace maganin na tsawon minti 4. An yi jiƙa kurkure sau uku na minti 1 kowanne a cikin ruwan deionized tsakanin kowace jiƙa don cire polymer ɗin da aka haɗa. An daidaita ƙimar pH na maganin haɗuwa da ruwan kurkure zuwa pH 2.0. Ana nuna fina-finan da aka shirya kamar haka (CE/PAA)n, inda n ke nuna zagayowar haɗuwa. (HEC/PAA)40, (MC/PAA)30 da (HPC/PAA)30 galibi an shirya su.
Halayyar Fim:
An yi rikodin kuma an yi nazarin spectra masu haske kusan na al'ada ta amfani da NanoCalc-XR Ocean Optics, kuma an auna kauri na fina-finan da aka sanya a kan silicon. Tare da wani abu mai santsi na silicon a matsayin bango, an tattara FT-IR na siririn fim ɗin da ke kan silicon a kan na'urar spectrometer ta Nicolet 8700.
Hulɗar haɗin hydrogen tsakanin PAA da CEs:
Haɗa HEC, MC da HPC tare da PAA cikin fina-finan LBL. An nuna siginar infrared na HEC/PAA, MC/PAA da HPC/PAA a cikin hoton. Ana iya ganin siginar IR mai ƙarfi na PAA da CES a sarari a cikin siginar IR na HEC/PAA, MC/PAA da HPC/PAA. Siginar FT-IR na iya nazarin haɗakar haɗin hydrogen tsakanin PAA da CES ta hanyar sa ido kan canjin madaurin sha na halaye. Haɗin hydrogen tsakanin CES da PAA galibi yana faruwa ne tsakanin iskar oxygen hydroxyl na CES da ƙungiyar COOH na PAA. Bayan an samar da haɗin hydrogen, ja mai shimfiɗawa yana canzawa zuwa alkiblar ƙarancin mita.
An lura da kololuwar 1710 cm-1 ga foda mai tsarki na PAA. Lokacin da aka haɗa polyacrylamide a cikin fina-finai tare da CEs daban-daban, kololuwar fina-finan HEC/PAA, MC/PAA da MPC/PAA sun kasance a 1718 cm-1, 1720 cm-1 da 1724 cm-1, bi da bi. Idan aka kwatanta da foda mai tsarki na PAA, tsawon kololuwar fina-finan HPC/PAA, MC/PAA da HEC/PAA sun canza da 14, 10 da 8 cm-1, bi da bi. Haɗin hydrogen tsakanin iskar oxygen ta ether da COOH yana katse haɗin hydrogen tsakanin ƙungiyoyin COOH. Ƙarin haɗin hydrogen da aka samar tsakanin PAA da CE, mafi girman canjin kololuwar CE/PAA a cikin siginar IR. HPC yana da mafi girman matakin haɗakar haɗin hydrogen, PAA da MC suna tsakiya, kuma HEC shine mafi ƙanƙanta.
Halayyar girma na fina-finan haɗin gwiwa na PAA da CEs:
An binciki halayen samar da fim na PAA da CEs yayin haɗa LBL ta amfani da QCM da spectral interferometry. QCM yana da tasiri don sa ido kan ci gaban fim a wurinsa a lokacin zagayowar haɗuwa ta farko. Spectral interferometers sun dace da fina-finan da aka girma sama da zagaye 10.
Fim ɗin HEC/PAA ya nuna ci gaban layi a duk tsawon tsarin haɗa LBL, yayin da fina-finan MC/PAA da HPC/PAA suka nuna ci gaban da ya fi girma a farkon matakan haɗuwa sannan suka rikide zuwa ci gaban layi. A yankin haɓaka layi, mafi girman matakin rikitarwa, mafi girman ci gaban kauri a kowane zagayen haɗuwa.
Tasirin pH na maganin akan girman fim:
Darajar pH na maganin yana shafar girman fim ɗin polymer da aka haɗa da hydrogen. A matsayinsa na mai rauni na polyelectrolyte, PAA za a yi masa ionized kuma a caji shi da rashin kyau yayin da pH na maganin ke ƙaruwa, ta haka ne zai hana haɗin hydrogen. Lokacin da matakin ionization na PAA ya kai wani mataki, PAA ba zai iya haɗuwa cikin fim ɗin da ke ɗauke da masu karɓar haɗin hydrogen a cikin LBL ba.
Kauri fim ɗin ya ragu tare da ƙaruwar pH na maganin, kuma kauri fim ɗin ya ragu ba zato ba tsammani a pH2.5 HPC/PAA da pH3.0-3.5 HPC/PAA. Muhimmin ma'aunin HPC/PAA shine kusan pH 3.5, yayin da na HEC/PAA shine kusan 3.0. Wannan yana nufin cewa lokacin da pH na maganin haɗuwa ya fi 3.5, ba za a iya samar da fim ɗin HPC/PAA ba, kuma lokacin da pH na maganin ya fi 3.0, ba za a iya samar da fim ɗin HEC/PAA ba. Saboda matakin haɗakar hydrogen na membrane na HPC/PAA, ƙimar pH mai mahimmanci na membrane na HPC/PAA ya fi na membrane na HEC/PAA. A cikin maganin da ba shi da gishiri, ƙimar pH mai mahimmanci na hadaddun da HEC/PAA, MC/PAA da HPC/PAA suka samar sun kasance kusan 2.9, 3.2 da 3.7, bi da bi. Mahimmin pH na HPC/PAA ya fi na HEC/PAA, wanda ya yi daidai da na membrane na LBL.
Aikin sha ruwa na membrane na CE/PAA:
CES tana da wadataccen rukunin hydroxyl don haka tana da kyakkyawan shaƙar ruwa da riƙe ruwa. Idan aka ɗauki membrane na HEC/PAA a matsayin misali, an yi nazarin ƙarfin shaƙar membrane na CE/PAA mai haɗin hydrogen zuwa ruwa a cikin muhalli. An siffanta shi da interferometry na spectral, kauri fim ɗin yana ƙaruwa yayin da fim ɗin ke shan ruwa. An sanya shi a cikin yanayi mai ɗanɗano mai daidaitawa a 25°C na tsawon awanni 24 don cimma daidaiton shaƙar ruwa. An busar da fina-finan a cikin tanda mai injin tsotsa (40°C) na tsawon awanni 24 don cire danshi gaba ɗaya.
Yayin da danshi ke ƙaruwa, fim ɗin yana yin kauri. A cikin yankin danshi mai ƙarancin kashi 30%-50%, girman kauri yana da jinkiri. Lokacin da danshi ya wuce kashi 50%, kauri yana girma da sauri. Idan aka kwatanta da membrane na PVPON/PAA mai haɗin hydrogen, membrane na HEC/PAA zai iya shan ƙarin ruwa daga muhalli. A ƙarƙashin yanayin danshi mai kusan kashi 70% (25°C), kauri na fim ɗin PVPON/PAA yana kusan kashi 4%, yayin da na fim ɗin HEC/PAA yana da kusan kashi 18%. Sakamakon ya nuna cewa duk da cewa wasu adadin ƙungiyoyin OH a cikin tsarin HEC/PAA sun shiga cikin ƙirƙirar haɗin hydrogen, har yanzu akwai adadi mai yawa na ƙungiyoyin OH da ke hulɗa da ruwa a cikin muhalli. Saboda haka, tsarin HEC/PAA yana da kyawawan halaye na sha ruwa.
a ƙarshe
(1) Tsarin HPC/PAA wanda ke da mafi girman matakin haɗin hydrogen na CE da PAA yana da saurin girma a cikinsu, MC/PAA yana tsakiya, kuma HEC/PAA shine mafi ƙasƙanci.
(2) Fim ɗin HEC/PAA ya nuna yanayin girma mai layi a duk tsawon lokacin shirye-shiryen, yayin da sauran fina-finai biyu MC/PAA da HPC/PAA suka nuna ci gaba mai girma a cikin zagayen farko, sannan suka canza zuwa yanayin girma mai layi.
(3) Girman fim ɗin CE/PAA yana da matuƙar dogaro da pH na maganin. Idan pH na maganin ya fi mahimmin matsayi, PAA da CE ba za su iya haɗuwa su zama fim ba. Tabon CE/PAA da aka haɗa ya narke a cikin babban pH na maganin.
(4) Tunda fim ɗin CE/PAA yana da wadataccen sinadarin OH da COOH, maganin zafi yana sa ya haɗu. Famfon CE/PAA mai haɗin giciye yana da kyakkyawan kwanciyar hankali kuma ba ya narkewa a cikin ruwan pH mai yawa.
(5) Fim ɗin CE/PAA yana da kyakkyawan ƙarfin sha ruwa a cikin muhalli.
Lokacin Saƙo: Fabrairu-18-2023