Structure-Property Evaluation of Photocured Homopolymers from Commercial and Experimental Dimethacrylates

Published

October 12, 2021

Author(s)

J Tanka, J W. Stansbury

Abstract

The development of new monomers that provide hydrophobic polymeric networks is under investigation with the goal of increasing the long-term durability of dental resins and composites. A variety of novel semifluorinated and hydrocarbon-based dimethacrylate monomers have been prepared. Properties including conversion, water sorption, water contact angle, flexural strength and Knoop hardness have been determined for the experimental photocured homopolymers as well as for a variety of polymers derived from commercial monomers commonly employed in dental materials applications. The later are included to aid in the development of structure-property relationships. Several of the experimental polymers, including most of those from the fluorinated monomers and one from a hydrocarbon-based monomer, exhibited extreme hydrophobicity (water sorption mass fractions of = 0.25 %), while only the polymers from the commercially available C12 and C14 a,?-diol dimethacrylates yielded similarly low levels of water uptake. Water sorption was analyzed both gravimetrically and by near infrared (NIR) spectroscopy with excellent agreement obtained between the two techniques. The extent of methacrylate conversion as a function of irradiation time was also measured with a NIR technique. A direct relationship between the ultimate degree of conversion and the number of atoms in flexible segments of the monomers was evident. Excellent correlations were obtained between the calculated hydrophilic-lipophilic balance (HLB) of the monomers and the measured values of water sorption and water contact angle for the polymers. One exception to this trend was found with an experimental hydrocarbon dimethacrylate, which was predicted to have very low water uptake due to a C16 side chain; however, the polymer exhibited significant water uptake with unusually rapid hydration/dehydration kinetics, presumably due to a unique network morphology. Compared with the excellent mechanical property results characteristic of the conventional dimethacrylates used in dentistry, such as Bis-GMA, urethane dimethacrylate and triethylene glycol dimethacrylate, several of the experimental fluorinated polymers produced acceptable alternatives. None of the experimental hydrophobic hydrocarbon monomers provided polymers that were comparable in strength to the conventional materials. However, the use of monomers, which may lack adequate homopolymer mechanical strength, as hydrophobic diluent comonomers in dental resins appears quite promising. A good correlation was observed between the amount of bending displacement prior to failure in the flexural strength test and the proportion of flexible segments in the monomers. Polymer networks that are able to combine hydrophobicity with good mechanical strength properties may potentially extend both the performance and the service lifetime of dental materials.

Citation

International Symposium on Advanced Materials With Biomedical Applications

Pub Type

Journals

Keywords

dental materials, dimethacrylates, fluorinated polymers, hydrophobic polymers, photopolymerization

Citation

Tanka, J. and Stansbury, J. (2021), Structure-Property Evaluation of Photocured Homopolymers from Commercial and Experimental Dimethacrylates, International Symposium on Advanced Materials With Biomedical Applications (Accessed July 27, 2024)