Editing Molecular electronics (section)

==Molecular materials for electronics==
{{further|Conductive polymer|Organic electronics}}

[[File:ConductivePoly.png|300px|thumb|Chemical structures of some conductive polymers. From top left clockwise: [[polyacetylene]]; [[Poly(p-phenylene vinylene)|polyphenylene vinylene]]; polypyrrole (X = NH) and [[polythiophene]] (X = S); and [[polyaniline]] (X = NH/N) and [[Poly(p-phenylene sulfide)|polyphenylene sulfide]] (X = S).]]

The biggest advantage of conductive polymers is their processability, mainly by [[Dispersion (chemistry)|dispersion]]. Conductive polymers are not [[plastic]]s, i.e., they are not thermoformable, yet they are organic polymers, like (insulating) polymers. They can offer high electrical conductivity but have different mechanical properties than other commercially used polymers. The electrical properties can be fine-tuned using the methods of [[organic synthesis]]<ref name=Ullmann>{{cite book |doi=10.1002/14356007.a21_429 |chapter=Polymers, Electrically Conducting |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2000 |last1=Naarmann |first1=Herbert |isbn=978-3-527-30673-2 }}</ref> and of advanced dispersion.<ref name=nalwa/>

The linear-backbone polymers such as [[polyacetylene]], [[polypyrrole]], and [[polyaniline]] are the main classes of conductive polymers. Poly(3-alkylthiophenes) are the archetypical materials for [[Solar cell#Organic/polymer solar cells|solar cells]] and transistors.<ref name=Ullmann/>

Conducting polymers have backbones of contiguous sp<sup>2</sup> hybridized carbon centers. One valence electron on each center resides in a p<sub>z</sub> orbital, which is orthogonal to the other three sigma-bonds. The electrons in these delocalized orbitals have high mobility when the material is ''doped'' by oxidation, which removes some of these delocalized electrons. Thus the [[Conjugated system|conjugated]] p-orbitals form a one-dimensional [[electronic band structure|electronic band]], and the electrons within this band become mobile when it is emptied partly. Despite intensive research, the relationship between morphology, chain structure, and conductivity is poorly understood yet.<ref>Skotheim, T., Elsenbaumer, R., Reynolds, J., Eds.; Handbook of Conducting Polymers, 2nd ed.; Marcel Dekker, Inc.: New York, NY, USA, 1998{{page needed|date=February 2023}}</ref>

Due to their poor processability, conductive polymers have few large-scale applications. They have some promise in antistatic materials<ref name=Ullmann/> and have been built into commercial displays and batteries, but have had limits due to the production costs, material inconsistencies, toxicity, poor solubility in solvents, and inability to directly melt process. Nevertheless, conducting polymers are rapidly gaining attraction in new uses with increasingly processable materials with better electrical and physical properties and lower costs. With the availability of stable and reproducible dispersions, [[poly(3,4-ethylenedioxythiophene)]] (PEDOT) and [[polyaniline]] have gained some large-scale applications. While PEDOT is mainly used in antistatic applications and as a transparent conductive layer in the form of PEDOT and [[Sodium polystyrene sulfonate|polystyrene sulfonic acid]] (PSS, mixed form: PEDOT:PSS) dispersions, polyaniline is widely used to make printed circuit boards, in the final finish, to protect copper from corrosion and preventing its solderability.<ref name=nalwa>{{cite book |doi=10.1016/B978-012513760-7/50062-9 |chapter=Conductive polymers as organic nanometals |title=Handbook of Nanostructured Materials and Nanotechnology |year=2000 |last1=Wessling |first1=B. |volume=5 |pages=501–575 |isbn=978-0-12-513760-7 }}</ref> Newer nanostructured forms of conducting polymers provide fresh impetus to this field, with their higher surface area and better dispersability.

Recently supramolecular chemistry has been introduced to the field, which provide new opportunity for developing next generation of molecular electronics.<ref>{{cite journal |last1=Chen |first1=Hongliang |last2=Fraser Stoddart |first2=J. |title=From molecular to supramolecular electronics |journal=Nature Reviews Materials |date=September 2021 |volume=6 |issue=9 |pages=804–828 |doi=10.1038/s41578-021-00302-2 |bibcode=2021NatRM...6..804C |s2cid=232766622 }}</ref><ref>{{cite journal |last1=Yao |first1=Yifan |last2=Zhang |first2=Lei |last3=Orgiu |first3=Emanuele |last4=Samorì |first4=Paolo |title=Unconventional Nanofabrication for Supramolecular Electronics |journal=Advanced Materials |date=June 2019 |volume=31 |issue=23 |pages=1900599 |doi=10.1002/adma.201900599 |pmid=30941813 |bibcode=2019AdM....3100599Y |s2cid=205290060 |url=https://hal.archives-ouvertes.fr/hal-02130590/file/islandora_78509.pdf }}</ref> For example, two orders of magnitude current intensity enhancement was achieved by inserting cationic molecules into the cavity of pillar[5]arene.<ref>{{cite journal |last1=Li |first1=Xiaobing |last2=Zhou |first2=Siyuan |last3=Zhao |first3=Qi |last4=Chen |first4=Yi |last5=Qi |first5=Pan |last6=Zhang |first6=Yongkang |last7=Wang |first7=Lu |last8=Guo |first8=Cunlan |last9=Chen |first9=Shigui |title=Supramolecular Enhancement of Charge Transport through Pillar[5]arene-Based Self-Assembled Monolayers |journal=Angewandte Chemie International Edition |date=21 February 2023 |volume=62 |issue=19 |pages=e202216987 |doi=10.1002/anie.202216987 |pmid=36728903 |s2cid=256502098 }}</ref>