Degradable Crystalline Polyperoxides from Fatty Acid Containing Styrenic Monomers

Abstract

Vinyl polyperoxides, alternating copolymers of vinyl monomers and molecular oxygen, are highly viscous amorphous materials because of the flexible peroxy (−O− O−) bonds in the main chain. In this study, crystalline polyperoxides have been synthesized by oxidative radical polymerization of styrenic monomers having fatty acid moieties attached to the phenyl ring using molecular oxygen at 100 psi pressure. Determination of active oxygen contents in polyperoxides, 13 C NMR spectroscopy, and electron impact mass spectroscopy (EI-MS) confirmed alternating placement of −O−O− bonds after every styrenic monomer unit in the copolymer main chain. Thermal stability was studied by thermogravimetric analysis (TGA). Exothermic degradation of these polyperoxides was observed by differential scanning calorimetry (DSC), and degradation products have been identified from EI-MS study. DSC and powder X-ray diffraction (PXRD) studies revealed crystallinity in the polyperoxides with fatty acids having 12 carbon atoms or longer. This crystalline behavior was further supported by polarized optical microscopy (POM), where a birefringence texture which is characteristic of semicrystalline polymer was formed for polyperoxides with C ≥ 12 of the side-chain alkyl carbons. Transmission electron microscopy (TEM) was used to define the thickness and crystal structure of the polymers. Theoretical studies have been performed using density functional theory (DFT) to support the experimental interlamellar distance from X-ray diffraction studies.

Composition‐dependent crystallization behavior of copolyperoxides from methyl methacrylate and 4‐vinylbenzyl stearate

“…Crystalline behavior of n‐alkyl methacrylate based polymers having number of side chain alkyl carbons C ≥ 12 was established by Hempel et al Polyperoxides from 4‐vinylbenzyl fatty esters showed crystalline behavior when the fatty acid moieties had alkyl chains with C ≥ 12 . In the present study, we determined the effect of MMA content on the crystalline behavior of the copolyperoxides from VBS and MMA monomers.…”

“…MMA (Sigma, 99%) was purified just before the polymerization reaction, by passing through an alumina oxide column to remove inhibitors. Side‐chain SA containing monomer 4‐vinylbenzyl stearate (VBS), was synthesized following previously reported literature . The 2,2′‐azobisisobutyronitrile (AIBN, Sigma, 98%) was purified from methanol by recrystallization.…”

“…In this regard, the utilization of crystallizable n‐aliphatic long chains can be an effective way to incorporate crystalline properties in the synthesized polyperoxide materials. Recently, we have reported a series of crystalline polyperoxides from fatty acid appended styrene monomers which were found to be of solid powdery nature, enabling their facile quantitative handling . We established that the crystalline behavior in these polyperoxides appeared when the fatty acid moieties had alkyl chains with C ≥ 12, and maximum crystalline melting temperature ( T m ) was obtained for the polyperoxide from 4‐vinylbenzyl stearate (VBS).…”

Regiospecificity of Alternating Copolymerization of Cyclic Conjugated Dienes and Oxygen

“…Polyperoxides, which include a labile OO bond in their main-chain repeating unit, are produced from vinyl and conjugated diene monomers in the presence of molecular oxygen by a conventional radical alternating copolymerization process. 1,2 Due to a readily degradable nature, the polyperoxides have been applied to various degradable functional materials such as dismantlable adhesives, 36 drug delivery system, 7 biodegradable materials, 8 fatty acid-containing crystalline polymers, 9 and property changeable thin films. 10,11 The polyperoxides obtained from sorbic esters have a highly regular chain structure consisting of an exclusive 5,4-unit as the alternating repeating diene unit (Figure 1(a)).…”

“…PP-CPD and PP-Fu readily degraded upon heating with a significant exothermic heat evolution, which is typically observed for polyperoxides. 9,12,14 The 5% weight loss temperature (T d5 ) and the maximum decomposition temperature (T max ) were T d5 = 129°C and T max = 169°C for PP-CPD, and T d5 = 88°C and T max = 133°C for PP-Fu. These values are approximately in the temperature Figure 5.…”