Influence of Crosslinker Concentration on Properties of Shape Memory Poly(cyclooctene) (PCO).

open_access
Open Access
Author:
Roettger, Karoline
Area of Honors:
Chemical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
Patrick Mather, Thesis Supervisor
Ali Borhan, Thesis Honors Advisor
Keywords:
Shape memory polymers (SMPs)
Polycyclooctene (PCO)
Dicumyl peroxide (DCP)
Thermomechanical properties
Crosslink density
Biomedical applications
Abstract:
This thesis investigates the influence of crosslinker concentration, dicumyl peroxide (DCP), on the thermal, mechanical, and shape memory properties of polycyclooctene (PCO), a semicrystalline elastomer with potential biomedical applications. By varying the amount of dicumyl peroxide (DCP) used during processing, polymer networks with different crosslink densities were synthesized and characterized. Thermal properties were examined through differential scanning calorimetry (DSC), while dynamic mechanical analysis (DMA) was used to quantify storage modulus, loss modulus, and shape memory performance. Gel fraction measurements confirmed successful network formation and helped form the most efficient network by removing loose chains. The results show that increasing crosslink density decreases the degree of crystallinity, lowering the observed melting temperature while simultaneously enhancing mechanical recovery. DMA data demonstrated that higher DCP content led to improved shape recovery, with the most crosslinked samples exhibiting greater actuation strength and more complete recovery cycles. However, increased crosslinking also broadened hysteresis and slowed crystallization kinetics, suggesting a trade-off between recovery efficiency and responsiveness. Isothermal crystallization experiments further revealed that elongation is highly sensitive to small changes in temperature, showing the complex relationship between crosslink density, applied stress, and thermal conditions. One promising area of application is the development of adaptive biomedical casting materials, particularly for pediatric clubfoot treatment, where tunable stiffness and controlled shape recovery are advantageous. Beyond biomedical devices, this work contributes to the broader field of shape memory polymers by demonstrating how crosslinking chemistry can be used to trigger both thermal transitions and mechanical response.