단일 분자 수준에서 순환 고분자의 합성 및 용융 상태에서 그들의 확산 운동의 특성
Summary
합성 및 단일 분자 수준에서 순환 고분자의 확산 움직임의 특성에 대한 프로토콜이 제공됩니다.
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
Representative Results
Discussion
4 무장과 8 모양의 중합체. 합성을위한 중요한 단계 인 ESA-CF 프로토콜 (그림 1)을 통해 제조 12, 24 단관 능성과 관능 성 선형 폴리 (THF)의 N -phenylpiperidinium 말 단기와이었다 하였다 위의 절차에 따라 합성. 11 이온 교환 복실 과잉 량을 함유하는 수용액에 트리 플레이트 카운터 음이온을 가진 폴리머 전구체의 아세톤 용액으로 재침을 실시 하였다.
<p class="jove_conte…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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