Date of Award

December 2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Guodong Du

Abstract

The development of degradable polymers has emerged as a significant focus within academic research, driven by increasing concerns over non-degradable waste. Previous studies showed the ability to degrade the Si-O-C bond in mild conditions, which was further taken into medical applications. The slow degradation time of the linear polymers and their nanoparticles in mild conditions led us to pursue two different solution paths. In this work we looked at hyperbranched poly(silyl ether)s A2+B3 and A2A’+B3 methodologies and silyl ester containing polymers. Hyperbranched polymers show potential in drug delivery applications as they are capable of loading more of the drug and releasing them faster. Silyl esters were studied previously and found to have faster degradation than silyl ethers. Hyperbranched polymers possess extensive surface areas, rendering them particularly suitable for nanoparticle formation, drug encapsulation, and polymer functionalization. The polymers are synthesized and subjected to characterization using NMR spectroscopy assess connectivity and branching. In this work we used 1H, 13C inverse gated, HSQCHC, HSQCHSi, HMBCHC, HMBCHSi, and HOESY NMR to differentiate the units of the polymers and calculate their degree of branching. The first system we studied was A2+B3, where we learned that varying the ratio of the two controls branching of the polymers. Our results showed that we were able to add excess SiH and OH groups to the backbone of the polymers for further functionalization. This was illustrated by end-capping the SiH groups with varying mono alcohols which can be changed based on applications. This idea led us to the A2A’+B3 system, where the A’ and the A2 groups are in competition. This led to lower branching, with a handle on the polymer for different applications. Poly(silyl ether-ester)s are prepared through a novel ring-opening reduction of cyclic anhydrides and hydrosilanes. This technique facilitates the transformation of symmetrical cyclic anhydrides into protected asymmetrical hydroxy-acids. We began with the reduction by tertiary hydrosilanes to form monomers, establishing the reaction and learning about the reaction, optimized conditions and the yields. Ring opening reductive polymerization was further derived, using dihydrosilanes and dihydro disilanes in order to form polymers containing silyl esters in the backbone. The polymers were found to have good thermal stability with two degradation peaks above 300 and 500 C coming from the silyl ethers and esters respectively. The polymers showed to degrade within six hours in the presence of water. The polymers showed the same propertied as previous works, differing in high yields, faster reactions, higher molecular weights, non-metal catalysts, and high efficiency. The carbonyls containing in the polymers can further be reduced by hydrosilanes, leading to hyperbranching. Further reduction occurs to the carbonyl leading to silyl acetal formations. Silyl acetals were found to degrade faster than esters and degrade at lower temperatures in comparison to silyl ethers and esters with temperatures around 200 C. Hyperbranched poly(silyl ether-silyl ester-silyl acetal)s were found capable of fully branching, reaching a degree of branching value of 1 while retaining their solubility. This is uncommon in A2+B3 systems, as the polymers retain solubility and the ability to gel in the presence of heat, typically 80 C. This work shows the ability to synthesize different degradable polymers with great potential in applications, both medical and industrial.

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