Thermosensitivity control of polyethlyenimine by simple acylation

Heejin Kim, Seonju Lee, Minwoo Noh, So Hyun Lee, Yeongbong Mok, Geun Woo Jin, Ji Hun Seo, Yan Lee

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


Branched polyethylenimine (b-PEI), an amine-rich polymer, can obtain thermosensitivity by a simple acylation reaction. The resulting N-acylated b-PEI derivatives showed a similar lower critical solution temperature (LCST) transition as their linear correspondent, poly(N-alkyloxazoline). Three acyl groups (propionyl, and isobutyryl, and n-butyryl) were introduced and resulted in LCSTs ranging from 10 °C to 90 °C depending on the structure and environment. The hydrophobicity of N-acylated b-PEI can be controlled by varying the acyl group and degree of acylation. Because the LCST transition is determined by the delicate balance between the hydrophobicity and hydrophilicity of the polymers, an increase of the hydrophobicity in N-acylated b-PEI lowers the transition temperature. Also, N-acylated b-PEI contains tertiary amines as well as unacylated primary or secondary amines which can be protonated during acidification from a pH of 7.4 to a pH of 5.5. The LCST transition was observed at elevated temperatures due to the increase of hydrophilicity by the protonation in the acidic environment. The LCST was also influenced by the salt concentration. A decrease of the LCST was observed as the NaCl concentration increased, probably due to the dominance of the salting-out effect. The very simple introduction of thermosensitivity into pre-existing polymers can be easily applied for the development of various dual or multiple signal-sensitive polymer systems.

Original languageEnglish
Pages (from-to)1367-1374
Number of pages8
Issue number6
Publication statusPublished - 2011 Mar 10
Externally publishedYes

Bibliographical note

Funding Information:
The authors thank Prof. Kazunori Kataoka of the University of Tokyo, for his kind discussion about the research. This work is supported by the Research Settlement Fund for new faculty of Seoul National University, the grant (2010-P2-14) of Advanced Institute of Convergence Technology (AICT), and the Basic Science Research Program (2010-0007118) through the National Research Foundation of the Ministry of Education, Science and Technology of Korea.


  • Acylation
  • Polyethylenimine
  • Thermosensitivity

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Materials Chemistry


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