Fluorescence techniques provide a vital platform for understanding fundamental biological processes for their tremendous advantages, i.e. super spatiotemporal resolution.

Water-soluble conjugated polymers are highly efficient at harvesting and emitting light energy. They can be used as bright fluorescent labels for imaging of biological cells and tissues. Based on the fluorescence signal modulation of the polymers in response to the analytes, it has driven interest in high-sensitive and rapid-response fluorescence biosensors.

Increasing needs for whole-body and in vivo cellular imaging bring about high requirements for diversity and stability of fluorescence probes. 

A range of conjugated polymers have been synthesized and cover overall visible light region, and prolong their emission to near-infrared (NIR) region. These polymers have good optical properties, excellent photostability, and low cytotoxicity.

Conjugated polymers also enable monitoring and tracing interaction of nanomaterials with living cells.

In vivo fluorescence imaging can be realized by using NIR fluorescence probe with deep tissue penetration ability.

Optical excitations of conjugated polymers generate bound excitons (electron–hole pairs) or free electronic carriers, which migrate independently throughout the polymer chain (molecular wires of chromophores). The interaction of conjugated polymers and the analytes can effectively interrupt the transportation of electrons or energy along the molecular wire. Thus, fluorescence of conjugated polymers is drastically changed by extremely low concentrations of electron donors, surfactants, and proteins. Thus it can track the dynamical change of the redox dopamine level in the physiological environment and releasing of the neurotransmitter in living dopaminergic neurons in response to  stimulation.

Small interfering RNA (siRNA) is double-stranded molecule that interferes the expression of specific genes with complementary sequences. Jicheng Yu and Sha Zhu reported conjugated polymer nanocarriers with core-shell structure for delivery and non-invasively tracking intracellular release of siRNA. The nanocarriers are capable of protecting siRNA from ribonuclease (RNase) and interacting with the negatively charged cell membranes, thus resulting in high transfection efficiency.

Ferroelectric polymers belong to an important family of functional materials which have thermodynamically stable spontaneous polarization states switchable by application of a sufficiently strong external electric field. Studies on the ferroelectric polymers are increasingly motivated by their exceptionally excellent electric properties. They are worth exploring as  bio-inspired photodetector for artificial retina, flexible wearable transducer for non-invasive and dynamic diagnosis of cardiovascular system, gate dielectrics in thin-film field-effect transistors (FETs), rewritable/non-volatile ferroelectric memories, electromechanical actuators, and high electric energy density capacitors.

Portable electronics are increasingly being used in numerous applications. Ferroelectric polymers are one of the most promising materials for flexible electronic devices.

They exhibit bi-stable polarization states that can be switched from one to the other by external electric field and can be retained after removal of the field.

Compared with the operation voltage of organic electronic devices (~10V), the minimum electric field (the coercive field) for switching polarization states of the ferroelectric polymers is usually too high, and thus there should be a reduction in the thickness of the polymer film.

Patterned thin films with various shapes and sizes can be fabricated by photolithography, which sheds new light on the integration of ferroelectric polymers into organic microelectronic devices. To achieve ultrahigh density (gigabits/inch^-2) information storage, ferroelectric polymer nanodot arrays can be fabricated through a facile, high-throughput, and cost-effective nanoimprinting method.

Ferroelectric Polymer Memory: Nonvolatile or Volatile？
Xianzhong Chen and Xin Chen reported ordered arrays of defect-modified ferroelectric polymer for data storage purpose. Nanoimprinting process leads to preferable orientation of polymer chains and delicately controlled distribution of the defects, and thus makes the memory nonvolatile.

Ferroelectric Polymers: High Energy Density Capacitors

Storage and release of electric energies of ferroelectric polymers are determined by polarization switching. To make the ferroelectric polymers more suitable for practical capacitors, it is natural to manipulate their crystal structures. Electric energy density as high as 22.5J/cm³, in comparison with 1-1.5J/cm³ for BOPP (Bi-axially Oriented Polypropylene) in commercial capacitors, is realized in crosslinked PVDF-based polymers.