Sains Malaysiana 55(3)(2026): 399-410

http://doi.org/10.17576/jsm-2026-5503-04

 

Nanofluids Comprising Lyotropic Side-Chain Liquid Crystalline Poly(6-(4-Cyanobiphenyl-4'-Yloxy)Hexyl Acrylate) in Deep Eutectic Solvents for Enhanced Thermal Energy Storage

(Nanobendalir yang Terdiri daripada Poli(6-(4-Sianobifenil-4'-Iloksi)Heksil Akrilat) Kristal Cecair Rantai Sisi Liotropik dalam Pelarut Eutektik untuk Penyimpanan Tenaga Terma yang Dipertingkatkan)

 

SYUKRINA IMTIYAZ ABDUL SAMAT^1,2, RUSLI DAIK^2,*, IRMAN ABDUL RAHMAN^3,4, HAIRUL A.A. HAMID⁵ & ERNIE SUZANA ALI⁶

 

¹Kolej PERMATA Insan, Universiti Sains Islam Malaysia, Bandar Baru Nilai, 71800 Nilai, Negeri Sembilan, Malaysia

²Department of Chemical Sciences, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

³Department of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

⁴Nuclear Technology Research Centre, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia

⁵School of Chemistry and Environment, Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia

⁶School of Applied Physics, Faculty of Science and Technology, Universiti Sains Islam Malaysia, Bandar Baru Nilai, 71800 Nilai, Negeri Sembilan, Malaysia

 

Received: 8 December 2025/Accepted: 4 February 2026

 

Abstract

Nanofluids have attracted attention for thermal transfer and energy storage due to their superior thermophysical properties. Conventional fluids such as water, ethylene glycol, and mineral oil suffer from low thermal conductivity, high vapor pressure, corrosion, and limited thermal stability, highlighting the need for more efficient heat transfer fluids. This study reports a novel nanofluid composed of a side-chain liquid crystalline polymer (SCLCP), poly(6-(4-cyanobiphenyl-4'-yloxy) hexyl acrylate) (P6ACB), and choline chloride-based deep eutectic solvents (DESs) with urea, glycerol, or ethylene glycol as hydrogen bond donors (HBDs). P6ACB was dissolved in a DES/N-methyl-2-pyrrolidone (NMP) mixture (10:90) at 2 wt.% and 6 wt.%. Thermophysical properties, including viscosity, thermal conductivity, and specific heat capacity, were measured. Viscosity increased with polymer content but decreased with temperature, exhibiting Newtonian behaviour above 13 s⁻¹, even in the mesophase at 90 °C. Thermal conductivity increased with polymer fraction due to enhanced molecular alignment, which also improved heat capacity. NDES2- and NDES3-based nanofluids with NMP-DES mixture, incorporating glycerol and ethylene glycol respectively, showed high thermal conductivity and specific heat capacity, indicating potential for thermal energy storage (TES) applications. Maximum thermal conductivity enhancements of 17.35% (NDES2) and 16.07% (NDES3) were observed at 50 °C and 2 wt.% polymer. NDES2 exhibited higher specific heat at lower temperatures, while NDES3 showed greater increases at higher temperatures. The results demonstrated that the hybridization of molecularly organized liquid crystalline polymer with DESs offers promising potential as alternatives for TES systems.

Keywords: Deep eutectic solvent; nanofluid; side-chain liquid crystalline polymer; specific heat capacity; thermal conductivity

 

Abstrak

Nanobendalir telah menarik perhatian aplikasi pemindahan haba dan penyimpanan tenaga kerana sifat termofizikal yang unggul. Cecair konvensional seperti air, etilena glikol dan minyak mineral mempunyai kekonduksian haba yang rendah, tekanan wap yang tinggi, kakisan dan kestabilan haba yang terhad, yang meningkatkan keperluan untuk bendalir pemindahan haba yang lebih cekap. Kajian ini melaporkan nanobendalir baharu yang terdiri daripada polimer kristal cecair rantai sisi (SCLCP), poli(6-(4-sianobifenil-4'-iloksi) heksil akrilat) (P6ACB) dan cecair campuran eutektik (DES) berasaskan kolina klorida dengan urea, gliserol atau etilena glikol sebagai penderma ikatan hidrogen (HBD). P6ACB telah dilarutkan dalam campuran DES/N-metil-2-pirolidon (NMP) (10:90) pada 2bt.% dan 6bt.%. Sifat termofizik, termasuk kelikatan, kekonduksian haba dan muatan haba tentu, telah diukur. Kelikatan meningkat dengan kandungan polimer tetapi menurun dengan suhu, menunjukkan sifat Newtonian melebihi 13s⁻¹, walaupun dalam mesofasa pada 90 °C. Kekonduksian haba meningkat dengan peratusan polimer disebabkan oleh penjajaran molekul yang dipertingkatkan, yang turut meningkatkan kapasiti haba. Nanobendalir berasaskan NDES2 dan NDES3 dengan campuran NMP-DES, masing-masing menggabungkan gliserol dan etilena glikol, menunjukkan kekonduksian haba dan kapasiti haba tentu yang tinggi, menunjukkan potensi untuk aplikasi penyimpanan tenaga haba (TES). Peningkatan kekonduksian haba maksimum sebanyak 17.35% (NDES2) dan 16.07% (NDES3) diperhatikan pada suhu 50 °C dan peratusan berat 2bt.%. NDES2 menunjukkan kapasiti haba tentu yang lebih tinggi pada suhu yang lebih rendah, manakala NDES3 menunjukkan peningkatan yang lebih besar pada suhu yang lebih tinggi. Keputusan menunjukkan bahawa hibridisasi polimer kristal cecair yang tersusun secara molekul dengan DES berpotensi sebagai alternatif dalam sistem TES.

Kata kunci: Cecair campuran eutektik; kekonduksian haba; muatan haba tentu; nanobendalir; polimer kristal cecair rantai sisi

 

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*Corresponding author; email: rusli.daik@ukm.edu.my