Controlled Rapid Formation of Polyurethane at 700 K: Thermodynamic and Kinetic Consequences of Extreme Photothermal Heating

Abstract

The photothermal effect of nanoparticles has proven to be an effective means of substantially increasing the rate of chemical transformations, by factors of up to 10 9 . For thermally activated processes, such a large increase in rate implies a corresponding increase in temperature large enough that it would be expected to affect the steady-state concentrations of products and reactants. We test this hypothesis by following the exothermic reaction between hexamethylene diisocyanate and poly-bis(triethylol) heptanedioate to produce a cross-linked polyurethane under both ambient and photothermal conditions. We demonstrate that the photothermal effect increases the reaction rate by a factor of 7.4 × 10 6 and decreases the effective equilibrium constant by a factor of at least 3 × 10 4 . These two changes provide kinetic and thermodynamic temperature estimates of 732 ± 21 and 683 ± 28 K, respectively. Remarkably, though both estimates of temperature are extreme, the chemical species produced under photothermal heating are the same as produced under ambient conditions.

Nanoscale heat for organic transformations: a photothermally driven retro Diels–Alder reaction

“…Though our AuNPs are small enough that they do not have a strong plasmonic feature coincident with the laser's wavelength (532 nm), our prior work has demonstrated their effectiveness for photothermal applications. Lear (2013, 2015), Fortenbaugh and Lear (2017), Burns and Lear (2019) Our current results also clearly establishes that the retro Diels-Alder reaction responds to photothermal heating by these particles.…”

“…It is also a degree of enhancement that is consistent with those we have reported for other reactions. Haas and Lear (2015), Fortenbaugh and Lear (2017) If normal Arrhenius behavior holds, the rate of the reaction should approximately double with every 10 K increase in temperature, implying photothermal temperatures of roughly 543 K. Such an extreme temperature estimate is also consistent with those given by ourselves Haas and Lear (2015), Fortenbaugh and Lear (2017), Burns and Lear (2019) and others Fasciani et al (2011) and appears to be a hallmark of photothermally driven reactions under intense light irradiation.…”

“…An emerging approach is to use the photothermal effect of nanoscale systems to provide molecularscale heat, which has been shown to yield large enhancements to the rate of chemical transformations. Johnson et al (2015Johnson et al ( , 2018, Lear (2013, 2015), Fortenbaugh and Lear (2017), Burns and Lear (2019), Fasciani et al (2011), Goodman et al (2017), Vetterlein et al (2018), Yamashita et al (2011), Garnett et al (2012), Barsic et al (2007), Boyd et al (2006), Abadeer and Murphy (2016), Duncan et al (2010) To date, our group's efforts have focused on applications in materials, where we have demonstrated the utility of photothermal heating for driving both the decomposition Johnson et al (2015Johnson et al ( , 2018, Haas and Lear (2013) and formation Haas and Lear (2015), Fortenbaugh and Lear (2017), Burns and Lear (2019) of polymers, while other groups have shown that photothermal heating can be used to generate and manipulate inorganic materials. Garnett et al (2012), Barsic et al (2007), Boyd et al (2006) Beyond materials-based systems, photothermal heating has also been shown to be an effective driver of small molecule Fasciani et al (2011), Goodman et al (2017), Vetterlein et al (2018), Yamashita et al (2011) and biological Abadeer and Murphy (2016), Duncan et al (2010) transformations.…”

Synthesis of Mono Ethylene Glycol (MEG)-Based Polyurethane and Effect of Chain Extender on Its Associated Properties

“…The peak at 1525–1529 cm −1 showed an amide II group [ 31 ], whereas the peak at 1531 cm −1 demonstrated an amide I [ 1 , 21 , 26 ]. Some of the interactions among the chains of the polyurethane polymer were due to the shift in the transmission peaks [ 45 ], including H–bonding between the C=O group and amine group of the polymer with the highest concentration of the cross-linker [ 33 ], dipole-dipole bonding in the C=O groups of the high concentration of the extender containing the polymer, as well as the induced dipole-dipole bonds that were formed between the aromatic rings of the polymer [ 21 , 26 ]. These outcomes showed that the hard polymer increasingly accumulated to make the domains in the polyurethane copolymer with an increase in hardness [ 34 ].…”

Asymmetries in the Electronic Properties of Spheroidal Metallic Nanoparticles, Revealed by Conduction Electron Spin Resonance and Surface Plasmon Resonance

“…Metallic nanoparticles are a fixture of modern science, where they provide a platform for a wide range of established and emerging technologies, including cancer treatment, − sensing, − and catalysis. − In all of these applications, it is the electronic structure and behavior of the nanoparticles that make them desirable. For example, metallic particles can possess a plasmon resonance that greatly enhances electric fields and allows single molecule sensing, provide hot electrons for electrocatalysis, , and provide rapid light-to-heat conversion for driving thermally activated chemical transformations. − Beyond plasmonic-based behaviors, the electronic structure of small particles can provide catalytic activity that differs greatly from bulk or atomic species. − The importance of nanoparticle electronic properties has motivated the development of a means to control and tune these properties. One of the most common means of doing so is through physical changes to the metallic core of the particles.…”