Sains Malaysiana 46(2)(2017): 309–315

http://dx.doi.org/10.17576/jsm-2017-4602-16

Dominant Influence of the Terminal Molecule of PNIPA Chain on Wettability

(Pengaruh Dominan Molekul Terminal Raintaian PNIPA ke atas Kebolehbasahan)

NURUL HUDA¹*, MOHD. RASHID² & NAHIDA SULTANA¹

¹Center for Advanced Research in Sciences, University of Dhaka, Dhaka 1000, Bangladesh

²Malaysia-Japan International Institute of Technology, 54100 UTM Kuala Lumpur,

Federal Territory, Malaysia

Received: 6 April 2016/Accepted: 8 June 2016

ABSTRACT

Poly(N-isopropylacrylamide) (PNIPA) brushes on silicon substrate was constructed and molecular weight and polydispersity index was controlled precisely. Molecular behavior of the PNIPA grafted surface was observed by using captive bubble contact angle method. A very interesting phenomenon of high density PNIPA grafted membrane with a chloride terminal molecule was observed. The contact angle of high density PNIPA-Cl increased sharply while the temperature rises above 32oC. But in the case of PNIPA gel surface the contact angle result decreases sharply while the temperature reaches above lower critical solution temperature (LCST). In order to identify the reason behind this abnormal behavior of PNIPA-Cl grafted membrane, the terminal chloride molecule of PNIPA chain was modified to less electronegative azide (-N3) as well as carboxylic acid (-COOH). Finally it was found that terminal molecule of high density PNIPA grafted membrane has a great influences on the wettability change of PNIPA membrane in water by changing the temperature.

Keywords: ATRP; grafted membrane; monomer; PNIPA

ABSTRAK

Berus poli(N-isopropilakrilamida) (PNIPA) pada substrat silikon telah dibina dan berat molekul serta indeks kepoliserakan telah dikawal dengan tepat. Tingkah laku molekul permukaan cantuman PNIPA telah diperhatikan dengan menggunakan kaedah sudut sentuhan tangkapan gelembung. Suatu fenomena yang sangat menarik untuk membran cantuman PNIPA ketumpatan tinggi dengan klorida terminal molekul diperhatikan. Sudut sentuh PNIPA-Cl ketumpatan tinggi meningkat dengan ketara manakala suhu meningkat melebihi 32oC. Tetapi dalam kes gel permukaan PNIPA, keputusan sudut sentuh berkurangan secara mendadak semasa suhu mencapai tahap di atas suhu kritikal larutan (LCST). Untuk mengenal pasti sebab di sebalik tingkah laku tidak normal daripada PNIPA-Cl membran cantuman ini, molekul klorida terminal rantaian PNIPA diubah suai untuk mengurangkan azida elektronegatif (-N3) serta asid karbosilik (-COOH). Kesimpulannya, didapati bahawa molekul terminal ketumpatan tinggi PNIPA membran cantuman mempunyai pengaruh yang besar pada perubahan kebolehbasahan membran PNIPA dalam air dengan mengubah suhunya.

Kata kunci: ATRP; grafted membran; monomer; PNIPA

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*Corresponding author; email: write2shakil@gmail.com