Doctor of Philosophy (Ph.D.)
Degree Granting Department
Jianfeng Cai, Ph.D.
Julie P. Harmon, Ph.D. (late)
Randy Larsen, Ph.D.
Shengqian Ma, Ph.D.
Sylvia Thomas, Ph.D.
Cationic polymerization, Ecofriendly, Lacquer, Radiation hard
In modern world research scopes are highly favored the areas of developing new polymer materials which are more integrated with the environment. Synthesizing eco-friendly, bio degradable polymer materials to replace petroleum based synthetic polymers to utilize in radiation hard applications is one of the main objectives of this study. 'Laccol' extracted from Vietnamese lacquer tree (Toxicodendron succedanea) polymerized with other monomers namely styrene and d-limonene (from citrus waste) respectively to develop copolymers via cationic polymerization. Laccol contains hydroxyl phenyl groups that act as radical scavengers, enhancing radiation resistance via their ability to convert excitation energy into non-chemistry inducing energy in lacquer that has been cured. Further, laccol based polyurethanes were synthesized which could possibly use as thermal insulator materials and as energy storing materials is another objective investigated in this study. All these developments are novel and reported firstly in the literature.
Lacquer saps are popular since ancient time periods because of its excellent toughness, high solvent resistivity and high durability. It contains two reactive hydroxyl groups in the phenyl ring and a C-17 unsaturated side chain at 3rd position of the phenyl ring. Due to the unsaturation of this C-17 side chain, it is a potent candidate for cationic polymerization process. Firstly, the proper method was developed to homo-polymerize laccol through cationic polymerization and procedure was further extended to produce copolymers of laccol:styrene and laccol:d-limonene using AlCl3.EtOAc as the cationic co-initiator. Trans conjugated double bonds in unsaturated side chain of laccol and terminal double bond in styrene or d-limonene was involved prominently during the chain growth polymerization. Synthesized materials were exposed to gamma radiation and alterations occurred due to irradiation process was studied. Specifically the material hardness differences, FTIR information, crosslinking density differences were investigated in addition to the other characterization techniques (DSC, TGA, Rheology Analysis, NMR, GPC, XRD). Further, laccol based novel polyurethanes were synthesized using three different diisocyanates groups (aliphatic; HMDI, cycloaliphatic; H12MDI, aromatic; 4,4'-MDI) and characterized the materials using above mentioned techniques.
Deterioration of the materials after expose to gamma radiation is problematic in industrial level operations (nuclear plants, medicinal sterilization plants) and space operations. Therefore, development of new radiation hard materials is essential with improved properties such as laccol:styrene copolymers we developed in this study. Though the petroleum based polymer materials play a major role in these fields, it is high time to replace them with eco-friendly materials such as d-limonene:laccol copolymers which possess promising radiation hard ability. Generation of citrus waste in industrial scale at yearly basis is becoming a major environmental concern nowadays. Therefore, development of radiation hard d-limonene:laccol copolymers could possibly be a good solution to this environmental concern as well. The copolymers wedeveloped in this study are promising candidates to serve as radiation shield or protective coatings in the high-tech industrial setup which are dealing with radiation such as nuclear reactors, medicinal sterilization plants and outer space operations.
The synthesized novel laccol based polyurethanes were characterized to identify their properties. Mainly, the influence of different diisocyanates, hydrogen bonding capability and crosslinking ability was investigated apart from other attributes. These analysis could provide broader understanding to synthesized novel PUs in future developments. Prepared novel PUs could possibly serve as thermal insulator materials in refrigerator coolant accessories, turbines and incinerators. Also it can be useful as an energy storing material.
Scholar Commons Citation
Marasinghe Arachchilage, Imalka, "Synthesizing Laccol Based Polymers/Copolymers and Polyurethanes; Characterization and Their Applications" (2021). USF Tampa Graduate Theses and Dissertations.