Characterization of Side-chain Liquid Crystalline Polypeptides - - PowerPoint PPT Presentation

Characterization of Side-chain Liquid Crystalline Polypeptides

Meghan Powers, Biology, Santa Barbara City College Katie Schaefer

• Prof. Edward Kramer
• Prof. Tim Deming

• Project Description

Characterization of the thermotropic mesogen and of the poly(L-lysine) backbone as separate components in order to understand the thermal dependence of liquid crystal transitions.

• Techniques

Differential Scanning Calorimetry Optical Microscopy

Liquid Crystals

Anisotropic: Having properties which vary depending on the direction of measurement. Birefringence: anisotropic optical properties a thermodynamic stable phase characterized by anisotropy

• f properties generally lying in the temperature range

between the solid and isotropic liquid phase

http://plc.cwru.edu/tutorial/enhanced/files/textbook.htm

Structure of Polypeptide

• Backbone: Lysine
• Spacer: (CH2)n n= 3,5,10
• Mesogen: liquid crystalline material

O O O C4H9O O OC4H9 O O

Spacer

Differential Scanning Calorimetry

http://www.psrc.usm.edu/macrog/dsc.htm

Polarized Optical Microscopy

Used to observe birefringence in crystalline or liquid crystalline materials in order to detect phase changes.

DSC Analysis of Mesogen

• 4
• 3
• 2
• 1

Heat flow W/g 200 150 100 50 Temperature (

• C)

Optical Analysis (10X) of Poly(Z-lys)

103°C 60°C 40°C 155°C 80°C 120°C

Characteristics of Mesogen

• Low temperature anisotropic phases

melt into isotropic liquid

• Formation of hard crystalline

structures after cooling

Characteristics of Poly(Z-lys)

• Hard glassy properties below glass

transition

• Structure becomes rubbery above

glass transition, no melting point

Characteristics of Homopolymers

• Glassy below Tg, rubbery above Tg
• Anisotropic liquid crystalline phases

characteristic of mesogen

• Thermal transitions are reversible

0.4 0.2 0.0

• 0.2
• 0.4

Heat flow (W/g) 150 100 50 Temperature (

• C)

PLM3 PLM5 PLM10

Side Chain LC Polypeptides

Future Plans

DSC on Poly(Z-lys) X-ray diffraction on components and homopolymers Synthesis of random copolymers of lysine and mesogenic lysine

Acknowledgments

Katie Schaefer Ed Kramer Krystyna Brzezinska The Kramer Group The Deming Group INSET

Polarized Optical Microscopy

Polarizer Incident Light Analyzer Image Support Sample Black Background Birefringence

Used to observe birefringence in crystalline or liquid crystalline materials in order to detect phase changes.

0.4 0.2 0.0

• 0.2

Heat flow W/g 120 110 100 90 80 Temperature (

• C)

10°C/min 5°C/min 1°C/min 93.8°C 95.5 °C 97.8 °C 103.2°C 103.0 °C 102.7 °C

DSC Rate Analysis of Plm-10