Research carried out in our Laboratory concern mechanisms of formation and stabilization of liquid crystal phases. In particular the analysis of the influence of many different factors (such as electric field, temperature, defects, polymer additives and surface interactions) on the physical properties of liquid crystals is performed. Our investigations include also the development of computer simulation methods to study soft matter particle systems.

The systems under investigation are such different mezophases as: nematics, smectics, cholesterics, frustrated chiral phases (TGB, BP), ferroelectric and antiferroelectric smectics, as well as cellulose-based liotropic superstructures. Investigations are focused on the description of structural, thermodynamic, optical, dielectric, electro-optic and visco-elastic properties of these phases as a function of frequency and strength of electric field, composition of material and temperature. Moreover, the modelling of the soft matter and simple liquids with computer simulation techniques (in particular, Molecular Dynamics MD, Brownian Dynamics BD, Monte Carlo MC) is carried out.

Examples of realized tasks

1. Structural, dielectric, visco-elastic and electro-optic properties of chiral liquid crystals (blue phases especially)
2. Self-organization in the systems of soft matter (liquid crystals, colloids)
3. Nonlinear dynamic effects in surface-stabilized liquid crystals
4. The influence of surface interactions on the physical properties of thin smectic liquid crystals
5. Development of computer simulations methods (MD, BD, MC): deterministic thermostats and simulations of strongly confined particle systems
6. Simulations of structural, thermodynamic and dynamic properties of soft matter and simple liquids systems
7. Investigation of layered LC/cellulose-type structures

Research projects

• The statutory project (2016 - 2018) - Physical properties of thin liquid crystal films - dr hab. A.C. Brańka, prof. IFM PAN
• NCN project (OPUS 13) - Elastic properties of liquid crystal blue phases (2018 - 2021), project leader - dr hab. A.C. Brańka, prof. IFM PAN
• NCN project (MINIATURA 1) - Preparation and characterization of nanocrystalline cellulose/liquid crystal systems (2017/2018), project leader -  dr inż. N. Bielejewska
• Participation in the LIDER project (Edition VII) carried out by the Wood Technology Institute - New biopolymer adhesives modified with silanes and ionic liquids for application in wood-based materials technology (2017 - 2019), main worker/ investigator - dr inż. N. Bielejewska
• NCN project (OPUS 3) - Stationary states in spatially limited microscopic systems: acoustic micro-voids and stimulated microgel molecules in microchannels (2013 - 2016), project leader - dr hab. A.C. Brańka, prof. IFM PAN
• MNiSW project - Identification of a new type of de Vries phase (2010 - 2014), project leader - dr hab. J. Hoffmann, prof. IFM PAN

Head of group

• Prof. Dr. hab. Arkadiusz Brańka

  phone: +48 61 86 95 239, room: 233

  e-mail: arkadiusz.branka@ifmpan.poznan.pl

The group

• Dr. Eng. Natalia Bielejewska

  phone: +48 61 86 95 273, room: 257, 225, 229, 249, 226

  e-mail: natalia.bielejewska@ifmpan.poznan.pl

• Dr. Eng. Dorota Dardas

  phone: +48 61 86 95 161, room: 225, 229, 249

  e-mail: dorota.dardas@ifmpan.poznan.pl

• Dr. Eng. Sławomir Pieprzyk

  phone: +48 61 86 95 164, room: 231, 265

  e-mail: slawomir.pieprzyk@ifmpan.poznan.pl

• M. Sc. Eng. Tetiana Yevchenko

  phone: +48 61 86 95 272, room: 253

  e-mail: tetiana.yevchenko@ifmpan.poznan.pl

Notable former group members

• Prof. Dr. hab. Wojciech Kuczyński

• Dr. hab. Jerzy Hoffmann, Prof. IFM PAN

• Dr. hab. Wojciech Jeżewski, Prof. IFM PAN

Photo

1. Equipment for investigations of the optical properties

1. Olympus Fluoview 1000 IX83 confocal microscope
   
   

   The dye molecules are excited using diode laser (λ = 473 nm) with the beam power equal to 1.24 mW. The fluorescence signal is detected in the spectral range 490 - 540 nm. A pinhole discriminates against the regions above and below the selected volume. The pinhole size is adjusted depending on magnification and numerical aperture of the objective.
   To obtain the 3D image of the whole sample, the focused beam scans the sample in the horizontal plane (xy-directions) and then mechanical refocusing at different depth (z-direction) in the sample and repeating the horizontal scanning. Each horizontal scan produces a thin ‘optical slice’ with thickness determined by the resolution of FCPM. The intensity of fluorescence as the function of coordinates is measured and stored in the computer memory.

2. Polarizing microscope BX53 firmy Olympus
   
   

   Experimental set-up for microscopic study of textures, phase transitions in temperature range 300 K–500 K with an accuracy of ± 0.01 K.

3. Spectrophotometer UV-VIS-NIR model V-670 (JASCO)
   
   

   Equipment for optical spectroscopy in wavelenght range 190-2700 nm.

4. Experimental set-up for investigations of birefringence of LC.
   (Hinds PEM 100 Photoelastic Modulator)
   
   

Equipment for dielectric measurements

Temperature range 300 K–500 K with an accuracy of ± 0.01 K.

1. Experimental setup I for dielectric and electrooptic measurements
   (Impedance Analyzer HP 4192A + Lock-in voltmeter SR 850).
   
   • frequency range for dielectric measurements - 5 Hz–10 MHz,
   • frequency range for electrooptic measurements - 5 Hz–100 kHz.
   
2. Experimental setup II for dielectric and electrooptic measurements
   (Impedance Analyzer Wayne Kerr 6440B + Lock-in voltmeter SR 530).
   
   • frequency range for dielectric measurements - 5 Hz–3 MHz,
   • measurements voltage 0.1 V – 10 V,
   • frequency range for electrooptic measurements - 5 Hz–100 kHz.
   
3. Experimental set-up III for investigations of spontaneous polarization and switching current of LC in frequency range
   • frequency range – 0.05 Hz–10 kHz,
   • measurements voltage - 2 V – 400 V.
   

Additional equipment

High speed video system Olympus i-SPEED 2

For each experimental setup, the Olympus high speed camera can be attached.
The speed of the microscopic image registration -2000-3000 frame/s.