Article Cite This: Macromolecules XXXX, XXX, XXX−XXX
pubs.acs.org/Macromolecules
Tandem Metathesis Polymerization-Induced Self-Assembly to Nanostructured Block Copolymer and the Controlled Triazolinedione Modification for Enhancing Dielectric Properties Jie Chen,† Ruyi Sun,† Xiaojuan Liao,† Huijing Han,† Yawei Li,*,‡ and Meiran Xie*,† †
School of Chemistry and Molecular Engineering and ‡Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241, China
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ABSTRACT: The efficient and versatile click chemistry based on 1,2,4-triazoline-3,5-dione (TAD) was used as one of the most potential postfunctionalizing pathways to specially design polymer nanostructure for dielectric materials. The block copolymer was synthesized by tandem ring-opening metathesis polymerization and metathesis cyclopolymerization and self-assembled into the core− shell nanostructure in the selective solvent, which could be modified by TAD in a controlled manner by tuning the TAD feeding amount, enabling the Alder−ene reaction of TAD with the double bonds to occur first on the polynorbornene backbone in the shell and then the cascade Alder−ene and Diels−Alder reactions on the polyacetylene backbone bearing five-membered rings in the core. The modified block copolymers incorporating varied amount of urazole moieties exhibited enhanced dielectric constant from 16.2 to 20.3 and lowered dielectric loss from 0.031 to 0.013 to 0.009, which provides a new idea of the selective postfunctionalization of nanostructures in solution for regulating the polymer structure and properties.
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nanostructure,10 superhelical nanotube,11 and core−shell nanoparticle7 in selective solvents without any post-treatment, and the conductive PA blocks are wrapped in the insulated PNBE blocks, which is very convenient for preparing polymeric molecular composites to further improve dielectric performance.10 However, compared to the traditional organic/ inorganic composites, in most cases, the low dielectric constant of polymeric materials based on these self-assembled nanostructures may be still difficult to meet the best proposal operation requirement of devices. To make up for the defect, one approach is to connect the polar molecules directly to the surface of nanostructures by the chemical modification to increase the dipole polarization without damaging the conduction domain inside the assemblies. 1,2,4-Triazoline-3,5-dione (TAD) as a polar molecule has a high dipole moment and can effectively react with many different functional aryl and unsaturated aliphatic groups in seconds under mild conditions without the requirement of catalysts, irradiation, or other external stimulus.12,13 The Diels−Alder and Alder−ene reactions based on TAD as one of the versatile click chemistry molecules have attracted more and more attention from engineering practice and academic field.14−18 Despite the large number of reports on the modification of different nanostructures previously by using click chemistry,19,20 the TAD-based click reaction is rarely used
INTRODUCTION Since the concept of click chemistry was introduced in 2001 by Sharpless and co-workers,1 the reactions as a modular synthetic approach have exerted a huge impact on the chemical community in the past decades due to the reliable and efficient synthesis of specially designed building blocks,2,3 which was applied widely to multiple research disciplines, especially in polymer chemistry and materials science. For example, in the dielectric energy storage research, Huang and co-workers have reported that a variety of polymers with high breakdown strength were covalently connected to the ferroelectric inorganic nanoparticles to build core−shell nanostructure by click chemistry,4 which eliminated the negative effect of ferroelectric on energy storage density and energy conversion efficiency of materials. The Grubbs catalyst-initiated ring-opening metathesis polymerization (ROMP)5 and metathesis cyclopolymerization (MCP)6 are the most noteworthy controlled polymerization techniques, which are used to produce a variety of well-defined polymers. Block copolymers consisting of polynorbornene (PNBE) segment and polyacetylene (PA) segment are easy to synthesize by one-pot tandem ROMP-MCP and exhibit the higher dielectric constant and stored/released energy density in comparison to the commercial polymeric capacitor film.7 Because of the sufficiently strong driving force such as π−π stacking of conjugated structure8 and the solubility difference between the constituent blocks in a solution, 9 these copolymers can be usually self-assembled into different nanostructures, such as nanocaterpillar,8 hollow sphere © XXXX American Chemical Society
Received: August 1, 2018 Revised: December 5, 2018
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DOI: 10.1021/acs.macromol.8b01645 Macromolecules XXXX, XXX, XXX−XXX
Article
Macromolecules
Scheme 1. Syntheses and TAD Modification of Random (a) and Block (b) Copolymers; Diagrammatic Sketch for the Controlled TAD Modification of Self-Assembled Core−Shell Nanostructure (c)
Table 1. Characteristics for Polymersa run
polymers
[TNP]:[SHD]:[EHD]:[Cat.]b
Mnc (kDa)
PDIc
1 2 3 4 5 6
PSHD PSHD80-co-PEHD20 PTNP25-b-PSHD25 PTNP50-b-PSHD25 PTNP100-b-PSHD25 PTNP25
0:100:0:1 0:80:20:1 25:25:0:1 50:25:0:1 100:25:0:1 25:0:0:1
21.7 16.7 30.7 49.2 12.6
1.23 1.06 1.08 1.07 1.18
Mnd (kDa)
240.4 903.2 1618.9
yield (%)
