Summary

Síntese de polímeros cíclicos e Caracterização do seu movimento difusivo no estado fundido na molécula de nível único

Published: September 26, 2016
doi:

Summary

Um protocolo para a síntese e caracterização de movimento difusivo de polímeros cíclicos no único nível molécula é apresentado.

Abstract

We demonstrate a method for the synthesis of cyclic polymers and a protocol for characterizing their diffusive motion in a melt state at the single molecule level. An electrostatic self-assembly and covalent fixation (ESA-CF) process is used for the synthesis of the cyclic poly(tetrahydrofuran) (poly(THF)). The diffusive motion of individual cyclic polymer chains in a melt state is visualized using single molecule fluorescence imaging by incorporating a fluorophore unit in the cyclic chains. The diffusive motion of the chains is quantitatively characterized by means of a combination of mean-squared displacement (MSD) analysis and a cumulative distribution function (CDF) analysis. The cyclic polymer exhibits multiple-mode diffusion which is distinct from its linear counterpart. The results demonstrate that the diffusional heterogeneity of polymers that is often hidden behind ensemble averaging can be revealed by the efficient synthesis of the cyclic polymers using the ESA-CF process and the quantitative analysis of the diffusive motion at the single molecule level using the MSD and CDF analyses.

Introduction

Cyclic polymers are unique in that they do not have chain ends. They often exhibit unusual behaviors which is distinct from their linear counterpart, including increased thermal stability of polymer micelles by a linear-to-cyclic conversion,1,2 and spatial organization of DNA in bacterial cells by a loop formation.3 Topological interactions between the cyclic chains are believed to be the critical factor for such unusual behaviors.4,5 Therefore, characterizing the motion and relaxation of cyclic polymers under entangled conditions has been an important research topic in polymer science for decades.6

Cyclic polymer dynamics has been investigated using both synthetic and naturally occurring molecules by means of ensemble averaged experimental methods such as nuclear magnetic resonance (NMR), light scattering, and viscosity measurements.7-9 However, these studies often suffer from impurity molecules in the samples.10 Furthermore, spatiotemporal heterogeneities of the motion of individual molecules caused by inherent structural heterogeneity of entangled polymers are often hidden behind the ensemble averaging in these studies. In order to characterize molecular level dynamics of cyclic polymers, a synthesis method that provides high purity cyclic polymers and an experimental and analysis methods that allow for quantitative characterization of molecular motion at the single molecule level have to be developed. Here, we will show a method to synthesize high-purity cyclic and dicyclic poly(THF)s that incorporate a fluorophore unit using an electrostatic self-assembly and covalent fixation (ESA-CF) process11-13 and a method to analyze the motion of the individual fluorophore-incorporated polymer chains using a combination of mean-squared displacement (MSD) and cumulative distribution function (CDF) analyses.

A proper data processing has been shown to be essential for the accurate characterization of the diffusive motion. With an adequate MSD and CDF analyses, a multiple-mode diffusion of the cyclic and dicyclic polymers in the melt and semi-dilute solution of the linear polymer chains has been revealed,14-16 suggesting the significant effects of the topological states of the polymers on the diffusive motion of the chains under entangled conditions.17 While the experimental and analytical approaches to characterize the motion of the cyclic polymers are described in this protocol, the same method can be used to quantitatively characterize the diffusive motion in many other heterogeneous systems. The approach would be especially suitable when multiple diffusion components existing in the samples are to be analyzed.

Protocol

1. Síntese de monofuncional e poli Bifuncional (THF) Poli monofuncional (THF) Chama seco num balão de fundo redondo de 2 tubuladuras de 100 ml. Vácuo e encher o balão com azoto (3 ciclos). Adicionar tetra-hidrofurano destilado (THF) (50 ml) ao balão. Colocar o balão num banho de água a 20 ° C e a temperatura equilibrar. Adicionar triflato de metilo (0,5 mmol) ao frasco por uma seringa. Agita-se a mistura durante 5-10 min a 20 ° C. Adiciona-se <e…

Representative Results

O perylene diimida-incorporada estrelas 4 armado e em forma de 8 poli dicíclico (THF) s foram sintetizados utilizando a auto-montagem eletrostática e fixação covalente (ESA-CF) processo (Figura 1, Figura 2). Imagens de fluorescência de molécula única de lapso de tempo foram medidos para o 4-armada (Figura 3a) e 8 em forma de polímeros (Figura 3B). As imagens de lapso de tempo de fluorescência (Figura 3)<…

Discussion

Os polímeros de 4-armados e moldaram-8 foram preparados por meio do protocolo SEC-CF (figura 1), que é um passo crítico para a síntese. 12,24 monofuncional e poli bifuncional linear (THF) com N s grupos terminais foram -phenylpiperidinium sintetizado de acordo com o procedimento anterior. 11 a permuta iónica foi realizada por reprecipitação de uma solução de acetona de um precursor de polímero com contra-aniões triflato, para uma solução aquosa contendo uma qu…

Divulgations

The authors have nothing to disclose.

Acknowledgements

This work was supported by a Grant-in-Aid for Scientific Research No. 22750122 (S.H.), No. 26288099 (T.Y.), and No. 23350050 (Y.T.) of the Japan Society for the Promotion of Science. S.H. is grateful for The Kurata Memorial Hitachi Science and Technology Foundation. The research reported in this publication was supported by the King Abdullah University of Science and Technology (S.H.).

Materials

Materials
THF Godo
Wakosil C-300 Wako Pure Chemical Industries
Acetone Godo
Toluene Godo
n-Hexane Godo
CHCl3 Kanto Chemical
Bio-Beads S-X1 Bio-Rad
Methyl triflate Nacalai Tesque
Triflic anhydride Nacalai Tesque
Potassium Hydroxide Wako Pure Chemical Industries
Ethanol Wako Pure Chemical Industries
Poly(tetrahydrofuran) Aldrich
Chloroform Wako Pure Chemical Industries
Immersion oil Cargille Type 37 / Type A
Equipment
2-Neck 100-mL round-bottom flask
Flask
Beaker
Funnel
Filter paper Whatman
Reflux condenser
Syringe
Water bath
Magnetic stirrer
Rotary evaporator
Microscope cover slips (24 x 24 mm, No. 1) Matsunami Glass CO22241
Staining jar AS ONE Corporation 1-7934-01
Ultrasonic cleaner VWR International  142-0047
Inverted microscope Olympus IX71
Ar-Kr ion laser Coherent Innova 70C
Berek compensator Newport 5540
Excitation filter Semrock LL01-488-12.5
Dichloric mirror Omega optical 500DRLP
Emission filter Semrock BLP01-488R-25
Lens and mirror Thorlabs
EM-CCD camera Andor Technology iXon
Objective lens (x100, N.A. = 1.3) Olympus UPLFLN 100XOP
Objective heater Bioptechs
Preparative GPC Japan Analytical Industry LC-908

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Habuchi, S., Yamamoto, T., Tezuka, Y. Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level. J. Vis. Exp. (115), e54503, doi:10.3791/54503 (2016).

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