Poly(Ethylene Glycol) (PEG) molecular weight, concentration, and exposure time effects on its surface properties : hydrophobicity and mechanical stiffness

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Poly(Ethylene Glycol) (PEG) molecular weight, concentration, and exposure time effects on its surface properties : hydrophobicity and mechanical stiffness


Author: Ng, Kenny
Title: Poly(Ethylene Glycol) (PEG) molecular weight, concentration, and exposure time effects on its surface properties : hydrophobicity and mechanical stiffness
Degree: M.Sc.
Year: 2012
Subject: Polyethylene glycol.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Health Technology and Informatics
Pages: x, 50 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2520214
URI: http://theses.lib.polyu.edu.hk/handle/200/6558
Abstract: The material of interest in this study is the highly versatile polymer, poly(ethylene glycol) (PEG). For a material to be utilized in a specific biomedical application, it would primarily depend on its traits (physical/mechanical or chemical), whether they can fulfill the needs of the operation. Among the many polymers available, there are definitely some that are more popular and capable than others, as their identities are established by their properties. As the most commonly used polymer within the biomedical industry, PEG's structure has given it an arsenal of unique features like high hydrophilicity / water content, high biocompatibility, high solubility, high protein rejection, high integration ability, lack of toxicity, and much more. In addition, its versatility is widely accepted due to the fact that most of these elements are tunable. However, the chemical fabrication parameters (combination of molecular weight and concentration) and also the physical parameters (sample's exposure time to the UV source, the intensity of the UV source, and the distance between them) that determine the outcome of PEG's qualities can be better understood. By improving comprehension of PEG's manufacturing process, the task of designing PEG for a specific task requiring specific properties can be facilitated more efficiently and with greater precision. The purpose of this study was to fabricate PEG with different molecular weights (526, 700 and 3400 daltons primarily) and at different concentrations (5 to 30% in intervals of 5) in an attempt to define their relationships relating its surface properties, which are composed of mechanical stiffness and hydrophobicity. PEG surface properties characterization was performed by measuring Young's modulus by the Instron apparatus, water contact angle by Ramehart goniometer, and by implementing a comparative analysis between PEG and polydimethylsiloxane (PDMS) results. This study also strived to overcome the challenge of synthesis and evaluation of PEG using inexpensive, yet simple techniques and machinery. Instead of employing chemical agents for PEG fabrication, UV polymerization will be implemented due to its ability to yield quick polymerization times and better bonding.
The results (all of which are independent samples) of this study indicate that each molecular weight of PEG requires a unique set of physical fabrication parameters. There is also no mechanical stiffness relationship across the different molecular weights (at least not between PEG MW 526, 700 and 3400). On the other hand, as PEG concentration increases within a set of PEG samples with the same molecular weight, hydrophobicity and mechanical stiffness increases. The peculiar finding regarding molecular weight and concentration was that, fabrication of PEG samples with molecular weight 526 and lower and concentrations of 15% and lower are extremely difficult. Just as there is a need for biomedical materials to have specific properties for an application, results demonstrate that there is also a need for an ideal molecular weight and concentration to fulfill that demand, depicted by the non-overlapping values of this study. This study was conducted in hopes of instigating new PEG research regarding molecular weights and concentration effects on the final products' properties. Ultimately, the findings proposed in this thesis may provide a general understanding of the mechanical stiffness or hydrophobicity properties to be expected under similar synthesis parameters, saving time and resources.

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