Gradient Sequence π-Conjugated Copolymers

Palermo, Edmund F.; McNeil, Anne J.

doi:10.1021/bk-2014-1170.ch019

Cited by 4 publications

(3 citation statements)

References 66 publications

(70 reference statements)

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“…The utility of CTP has already been demonstrated with the design of more complex architectures bearing π-conjugated segments including: graft, block, gradient, , star, and donor–acceptor polymers . Alternating copolymers have been explored using Kumada CTP, typically with thiophene dimers bearing different side-chain units, but extensions beyond dimers are scarce .…”

Section: Resultsmentioning

confidence: 99%

Conjugated Polymers with Repeated Sequences of Group 16 Heterocycles Synthesized through Catalyst-Transfer Polycondensation

et al. 2016

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Periodic π-conjugated polymers of the group 16 heterocycles (furan, thiophene, and selenophene) were synthesized with controlled chain lengths and relatively low dispersities using catalyst-transfer polycondensation. The optical gap and redox potentials of these copolymers were fine-tuned by altering the heterocycle sequence, and atomic force microscopy revealed nanofibrillar morphologies for all the materials. Grazing incidence wide-angle X-ray scattering of the thiophene-selenophene copolymers indicated that the π-stacking distance increased with incorporation of the larger heteroatom (from ∼3.7-4.0 Å), while the lamellar spacing decreased (from ∼15.8-15.2 Å). The study also revealed that periodic sequences allow electronic properties to be tuned while retaining nanofibrillar morphologies similar to those observed for poly(3-hexylthiophene).

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Section: Resultsmentioning

confidence: 99%

Conjugated Polymers with Repeated Sequences of Group 16 Heterocycles Synthesized through Catalyst-Transfer Polycondensation

et al. 2016

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“…The copolymerization of 2,5-dibromo-3-hexylthiophene and 2,5-dibromo-3-(6-bromohexyl)thiophene following a Grignard metathesis polymerization route yields low dispersity, regioregular, random copolymers (P3BrHT:P3HT) with controllable ratios (Table ). After precipitation, P3BrHT:P3HT copolymers can be redissolved and functionalized according to a Menshutkin amine quaternization, , yielding ionic liquid-like charge moieties randomly distributed along the polymers (P3BImHT:P3HT) at desired charge fractions ( f ionic ). Dilute solutions of the nearly monodisperse P3BImHT:P3HT copolymers of similar molecular weights (measured from both SEC and SANS, Table ) are prepared (3 mg mL –1 ) in deuterated solvents of marginal quality.…”

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confidence: 99%

Absence of Electrostatic Rigidity in Conjugated Polyelectrolytes with Pendant Charges

et al. 2019

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The delocalization of electrons in conjugated polymers impacts their chain shape, affecting their local ordering, self-assembly, and ultimately charge transport. Conjugated polyelectrolytes introduce electrostatic interactions as a molecular design parameter to potentially tune chain rigidity by combining the π-conjugated polymer backbone with pendant ionic groups. In conventional polyelectrolytes, the selfrepulsion of the bound charges induce extended rod-like chain configurations. Here, we leverage small-angle neutron scattering to measure the chain shapes of model conjugated polymers in dilute solution with controlled fractions of randomly distributed pendant charges. We find these model polythiophenes are semiflexible, with a persistence length of approximately 3 nm, regardless of charge fraction, suggesting the effective absence of electrostatic rigidity in conjugated polyelectrolytes. While the overall persistence length is negligibly impacted by pendant charges, optical spectroscopy indicates that the pendant charges increase the backbone torsion between thiophene rings without significantly impacting the π-conjugation length (the length of electron delocalization along a nearly planar backbone) in dilute solution. These results indicate the effective decoupling of the pendant ionic charges from the overall chain conformation with implications for solution processing of organic semiconductors.

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“…Gradient copolymers, which exhibit a gradual change in their composition from one end of the chain to the other, are of particular interest because they exhibit unique properties compared with their statistical, alternating and block copolymer counterparts [194]. The properties of a copolymer are not only determined by the monomer type and composition but is also strongly associated with the distribution of different monomer units along the polymer chains [64,117].…”

Section: Properties Of Gradient Copolymersmentioning

confidence: 99%

Understanding and controlling the structure of thin polymer films used in photolithography

Alam¹

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Line edge roughness (LER) is one of the major impediments to the semiconductor industry achieving the desired device performance and satisfying the goals set by International Technology Roadmap for Semiconductor (ITRS). LER is defined as any sort of unwanted roughness in semiconductor features, and among many other factors, structural heterogeneity of the photoresist materials is one of the sources of LER in photolithographic devices. This gives the motivation to study a new class of copolymer named 'gradient copolymer', which is unique in terms of the copolymer chain structure. The copolymer composition of gradient copolymers changes from one end of the chain to the other gradually, while the copolymer composition is on average constant along the chains for conventional statistical copolymers. In contrast, block copolymers show an abrupt switch in the polymer composition. In this study, statistical, block and gradient copolymers have been synthesized for two different monomer pairs (styreneacrylonitrile and hydroxystyrene t-butyl acrylate) using reversible addition-fragmentation chain transfer (RAFT) and conventional radical polymerization (CvRP) method, and their surface properties extensively studied.The kinetics of copolymerization of styrene (St) and acrylonitrile (AN) by RAFT method was studied in detail. Reactivity ratios of St and AN were determined for nine different feed compositions for RAFT, and the effect of solvent on reactivity ratios was discussed based on the bootstrap model. Batch polymerization of styrene (St) and acrylonitrile (AN) yielded statistical and spontaneous gradient copolymers depending on the monomer feed ratio, and the chain structures were confirmed from the change in the copolymer composition. St-and AN-centered triad distributions were determined using quantitative 13 C NMR. Using the continuous feeding approach, forced gradient St-AN copolymers were prepared, and St-block-AN copolymers synthesized by the chain extension method. Statistical, gradient and block copolymers have also been synthesized for the acetoxystyrenet-butyl acrylate monomer system. The statistical and gradient structures were confirmed from the change in the composition since this pair does not provide any well resolved peaks for different triad sequences in 13 C NMR. Hydroxystyrenet-butyl acrylate (HOST-tBA) copolymers were prepared by selective hydrolysis of 4-acetoxystyrenet-butyl acrylate (AOST-tBA) copolymers.The properties of the both copolymer systems were found to be strongly dependent on the copolymer structure. A unique broad glass transition was observed for the gradient copolymers, which is different from behaviour of the statistical and block copolymers. Surface properties of St-AN statistical, gradient and block copolymer thin films were found to be very different due to the

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Gradient Sequence π-Conjugated Copolymers

Cited by 4 publications

References 66 publications

Conjugated Polymers with Repeated Sequences of Group 16 Heterocycles Synthesized through Catalyst-Transfer Polycondensation

Conjugated Polymers with Repeated Sequences of Group 16 Heterocycles Synthesized through Catalyst-Transfer Polycondensation

Absence of Electrostatic Rigidity in Conjugated Polyelectrolytes with Pendant Charges

Understanding and controlling the structure of thin polymer films used in photolithography

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