Issue 14, 2011

Block sequence affects thermosensitivity and nano-assembly: PEG-l-PA-dl-PA and PEG-dl-PA-l-PA block copolymers

Abstract

We are reporting triblock copolymers of (ethylene glycol)44–(L-alanine)9–(DL-alanine)9 (PEG–L-PA–DL-PA) with α-helical L-PA localized between flexible PEG and DL-PA, and (ethylene glycol)44–(DL-alanine)9–(L-alanine)9 (PEG–DL-PA–L-PA) with gradient flexibility in water. Aqueous solutions of PEG–L-PA–DL-PA underwent only sol-to-gel transition, whereas those of PEG-DL-PA-L-PA underwent sol-to-gel-to-squeezed gel transitions as the temperature increased. The L-PAs of both polymers have an α-helical secondary structure in water at low temperature. However, the α-helical structure of the PEG-DL-PA-L-PA changed into a random coil structure as the temperature increased above 40 °C, whereas the PEG-L-PA-DL-PA kept the α-helical secondary structure over the same investigated temperature range of 4 °C to 50 °C. Cryo-transmission electron microscopy images and dynamic light scattering suggested that the PEG-L-PA-DL-PA develops spherical micelles, whereas the PEG-DL-PA-L-PA develops cylindrical bundles as well as spherical micelles in water. Even though both block copolymers have a similar composition of (ethylene glycol)44, (L-alanine)9, and (DL-alanine)9, they showed significantly different temperature-sensitivities as well as different nano-assemblies in water. This report suggests that the block sequence of a polymer is very important in developing a specific nano-structure as well as in controlling thermosensitivity of the polymer, thus providing useful molecular information in designing a biomaterial.

Graphical abstract: Block sequence affects thermosensitivity and nano-assembly: PEG-l-PA-dl-PA and PEG-dl-PA-l-PA block copolymers

Supplementary files

Article information

Article type
Paper
Submitted
24 Mar 2011
Accepted
03 May 2011
First published
08 Jun 2011

Soft Matter, 2011,7, 6515-6521

Block sequence affects thermosensitivity and nano-assembly: PEG-L-PA-DL-PA and PEG-DL-PA-L-PA block copolymers

S. H. Park, B. G. Choi, H. J. Moon, S. Cho and B. Jeong, Soft Matter, 2011, 7, 6515 DOI: 10.1039/C1SM05505D

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements