可視光応答型光触媒としてペリレンを使用した官能ビニルモノマーの原子移動ラジカル重合

Summary

A method for the atom transfer radical polymerization of functionalized vinyl monomers using perylene as a visible-light photocatalyst is described.

Abstract

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The procedure is performed under an inert atmosphere using air- and water-exclusion techniques. The outcome of the polymerization is affected by the ratios of monomer, initiator, and catalyst used as well as the reaction concentration, solvent, and nature of the light source. Temporal control over the polymerization can be exercised by turning the visible light source off and on. Low dispersities of the resultant polymers as well as the ability to chain-extend to form block copolymers suggest control over the polymerization, while chain end-group analysis provides evidence supporting an atom-transfer radical polymerization mechanism.

Introduction

The synthesis of technologically advanced polymers requires precise control over polymer molecular weight, dispersity (Ð), composition, and architecture.^1,2 Controlled radical polymerizations (CRPs)^3-8 have revolutionized the synthesis of well-defined polymers, with atom transfer radical polymerization (ATRP) being the most used CRP, largely due to operational simplicity and synthetic versatility.^9-14 The crux of ATRP is the ability to reversibly deactivate the polymerization, controlling the equilibrium between a propagating radical and a dormant species. Enforcing a low concentration of active radicals greatly minimizes bimolecular termination pathways and allows for the synthesis of well-defined polymers.

Traditional ATRP relies on a transition metal catalyst to mediate this equilibrium.³ These metal catalysts contaminate the polymer product and impede implementation in biomedical or electronic applications while also raising environmental concerns. Although significant strides have been made to reduce the catalyst concentration to ppm levels, these methodologies require more demanding experimental conditions and metal contamination is still not entirely eliminated.^15,16

Reversible addition-fragmentation transfer^17,18 and nitroxide-mediated polymerizations^19,20 are CRPs that do not require metal catalysts, although they have been used less often than ATRP.³ Recently, reversible chain-transfer²¹ and reversible complexation^22,23 variants of ATRP that can use organic catalysts were reported. However, these methodologies require the use of alkyl iodide initiators and are not effective with the alkyl bromides commonly employed in ATRP. A highly desirable CRP would match the performance, feasibility, and robustness of traditional ATRP while being catalyzed by an organic catalyst under mild conditions.

Here, we describe a methodology for the radical polymerization of functionalized vinyl monomers using perylene as a visible-light photocatalyst. Through optimization of parameters such as stoichiometry, concentration, time, and light flux, the molecular weight of the polymers can be controlled.^{24, 25} Similar methodologies have been recently introduced using phenothiazine derivatives as photocatalysts for metal-free ATRP.^{26, 27} Because researchers in the field of polymerization catalysis are constantly developing new catalytic systems, the ability to compare catalyst performance across a number of metrics is vital. This ability to make comparisons relies heavily upon procedural consistency and clarity on the part of the researchers performing the experiments. As such, it is our goal that this video will be used to help precisely communicate the methods by which these polymers are synthesized and characterized.

Protocol

注意：このプロトコルで使用される化学物質の多くは、有害物質です。化学物質等安全データシート（MSDS）を参照し、これらの物質を扱う際には、適切な個人用保護具（P​​PE）を使用します。 1.精製、準備、および試薬の保管製造業者のプロトコルに従って、溶媒精製システムを用いて使用される全ての溶媒を精製します。溶媒精製システムが使用できない場…

Representative Results

表1は、このメソッドを介して達成可能な重合結果の範囲を示しています。これらのデータは、ペリレンが官能ビニルモノマーの数の重合のための触媒として機能することが可能であることを示しています。特定のモノマー、溶媒、化学量論量、開始剤のような反応パラメーターの数のいずれかの調整、光源が非常に良いからではなく広い範囲の分子量及…

Discussion

プロトコルはこの重合法の具体例を示していたが、この反応を行う研究者が利用できるオプションはかなり広いです。修飾は、ATRPが実行されている特定のどんなphotoredoxの最適化を可能にするために、プロトコル全体点の個数で製造することができます。新しいモノマー、開始剤、及び調査下に来るこの反応のための触媒として、反応を実行するために使用される化学量論および溶媒は、反?…

Materials

perylene, min 98.0%	TCI America	TCP0078-025G	purify by sublimation
N,N-dimethylformamide	VWR	EM-DX1726-1	Omnisolv
methyl methacrylate, 99%	VWR	200000-678	distilled prior to use, stored in refrigerator
ethyl α-bromophenyl acetate	Aldrich	554065	distilled prior to use stored in refrigerator
butylated hydroxytoluene	Aldrich	W218405
Chloroform-D	Cambridge Isotope Labs	DLM-7-100
tetrahydrofuran	VWR	EM-TX0279-1	Omnisolv
methanol	VWR	BDH1135
dichloromethane	VWR	EM-DX0831-1	Omnisolv
styrene, 99%	VWR	AAAA18481-0F	distilled prior to use, stored in refrigerator
glass scintillation vial, 20 mL	VWR	66022-065
screw top vial, 2 mL	Agilent	5182-0715
septum cap for screw top vial	Agilent	5182-0717
heavy wall pressure vessel, 100 mL	Synthware	P160005
syringe, 1 mL norm-ject	VWR	89174-491
NMR tube	New Era	NE-UL5-7'
nylon syringe filter, 0.45 um	VWR	28143-240
glovebox	Mbraun	LABstar
solvent purification system	Mbraun	MB-SPS-800
stirplate	IKA	3582401
light-emitting diodes	Creative Lighting Solutions	CL-FRS1210-5M-12V-WH	2x 12-inch strips of 5500 K white LEDs were used for illumination
12V DC power supply for LEDs	Creative Lighting Solutions	CL-PS16001-40W
high performance liquid chromatograph	Agilent	G1310B, G1322A, G1329B, G1316A
gel permeation size-exclusion columns	Agilent	PL1110-6500
multi-angle light scattering detector	Wyatt	WTREOS
differential refractometer	Wyatt	WTREX