Electronic structure calculations of radical reactions for poly(methyl methacrylate) degradation

Conforti, Patrick F.; Garrison, Barbara J.

doi:10.1016/j.cplett.2005.02.124

Cited by 34 publications

(45 citation statements)

References 24 publications

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“…It is further assumed that partial particle disintegration of the MG-0 particles crosslinked with DEGDMA occurs mainly due to photolytic Norrish type I cleavage reactions of the ester bonds present in this molecule, rather than due to Norrish type II PMMA main chain degradation reactions. The latter are known to dominate at shorter wavelengths (157 nm) 231 than the ones used in the described experiment (>200 nm). Microgels prepared with a crosslinker, not containing any labile ester bonds connecting two polymer chains, should therefore exhibit an enhanced photo stability.…”

Section: Preparation and Characterization Of Crosslinked Photo-degradmentioning

confidence: 96%

“…This could be assigned to Norrish type side reactions, which are known to take place for wavelengths below 300 nm. [230][231] In addition, the curve obtained for the MG-0 particles does not follow an exponential decay. In this case, a degradation mechanism based on Norrish type reactions is assumed, since the simultaneous occurrence of several non-defined photoreactions leads to a different degradation profile compared to the photo-labile microgels.…”

Section: Preparation and Characterization Of Crosslinked Photo-degradmentioning

confidence: 99%

“…However, to degrade the crosslinkers and the resulting PMMA gel particles in a controlled manner under mild conditions, Norrish-type side reactions, which primarily take place for irradiations with wavelengths of < 300 nm, should be avoided. [230][231] UV-vis spectroscopy of the crosslinkers CL-1A -CL-3A shows in every case an absorption maximum at 260 nm accompanied by tailing up to 370 nm. In comparison, the spectrum of CL-4B shows the anticipated additional absorption maximum at 342 nm (see Figure 19b).…”

Section: Synthesis and Characterization Of Photo-labile Crosslinkersmentioning

confidence: 99%

“…Meaning, Norrish-type side reactions, which primarily take place for irradiations with wavelengths of < 300 nm [230][231] and undesirable side effects in biological applications should be avoided. UV-vis spectroscopy of the crosslinkers CL-4B and CL-5B showed in every case an absorption maximum at 300 nm and an additional absorption maximum at 342 nm.…”

Section: Dual Stimuli-responsive P(hema-co-maa) Microgels: Phdependenmentioning

confidence: 99%

“…PMMA (Norrish type II). [230][231] Since these reactions require harsh irradiation condition such as UV-C light, much effort has been paid to increase the photo-sensitivity of ester groups by the introduction of several chromophores. As an example, the attachment of pyrenylmethanol to polymeric backbones via an ester bond is worth mentioning.…”

Section: Types Of Chromophores In Polymeric Materialsmentioning

confidence: 99%

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Light-Sensitive Polymeric Nanoparticles Based on Photo-Cleavable Chromophores

Klinger

2013

Springer Theses

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This thesis focuses on the design, synthesis and characterization of novel photo-sensitive microgels and nanoparticles as potential materials for the loading and light-triggered release/accessibility of functional compounds. In order to realize this concept, different approaches to irradiation-dependent response mechanisms have been investigated.Novel light-cleavable divinyl functionalized monomeric crosslinkers based on o-nitrobenzyl derivatives were synthesized and used for the preparation of either PMMA or hydroxyl functionalized PHEMA microgels swellable and degradable in organic solvents. By the introduction of anionic MAA moieties into the PHEMA microgels, this concept was successfully transferred to double stimuli-responsive p(HEMA-co-MAA) hydrogel nanoparticles exhibiting a pH-dependent swelling and light-induced degradation behavior in aqueous media. This sensitivity to two orthogonal triggers is proposed to combine a pHinduced post-formation loading mechanism with a pH-and light-triggered release. In addition, a new class of enzyme-and light-sensitive PAAm microgels based on (meth-)acrylate functionalized dextrans as photo-and enzymatically degradable macromolecular crosslinkers was developed by introducing a photo-labile linker between the enzymatically degradable dextran chain and the polymerizable vinyl moieties. Here, the water solubility of the crosslinkers is assumed to enable an in situ loading approach of hydrophilic compounds.A different approach to the loading of microgels is based on photo-labile covalent microgel-drug conjugates. The first step to the realization of this concept was achieved by the development of a novel functional monomer consisting of a doxorubicin molecule covalently attached to a radically polymerizable methacrylate group via a photo-cleavable linker.Moreover, in order to enable the release of hydrophobic substances in aqueous media, hydrophobic nanoparticles consisting of a photo-resist polymer were designed to be degradable upon irradiation in water. Light-triggered conversion of the initial hydrophobic polymer into hydrophilic PMAA induced in situ particle dissolution and release of nile red.Since the introduction of a stimuli-responsive shell around a microgel is assumed to prevent leakage of embedded compounds, studies on non-stimuli-responsive shell formation around preformed microgel seed particles and the formation of microgel cores in polymeric shells were conducted to investigate potential synthetic pathways to this approach.In a last attempt, the surface of PHEMA and p(HEMA-co-MAA) microgels was functionalized with cinnamoyl groups in order to trigger the (reversible) particles interaction with each other by light-induced [2+2] cycloaddition reactions.

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Section: Preparation and Characterization Of Crosslinked Photo-degradmentioning

confidence: 96%

Section: Preparation and Characterization Of Crosslinked Photo-degradmentioning

confidence: 99%

Section: Synthesis and Characterization Of Photo-labile Crosslinkersmentioning

confidence: 99%

Section: Dual Stimuli-responsive P(hema-co-maa) Microgels: Phdependenmentioning

confidence: 99%

Section: Types Of Chromophores In Polymeric Materialsmentioning

confidence: 99%

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Light-Sensitive Polymeric Nanoparticles Based on Photo-Cleavable Chromophores

Klinger

2013

Springer Theses

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Norrish Type I Reaction

2010

Comprehensive Organic Name Reactions and Reagents

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The light‐initiated carbon‐carbon bond cleavage between the α‐carbon and the carbonyl of a ketone or an aldehyde to form an alkyl and an acyl radical pairs, from which a variety of products can be formed, such as alkane, alkene, cyclic acetal, decarbonyl compound, and oxetane and this reaction is referred to as the Norrish type I reaction. This reaction is initiated by a n‐π* excitation followed by an α‐cleavage to form an acyl and an alkyl radical pairs. It has been reported that this reaction is influenced by both the structure of the substrate and the reaction conditions, as evidenced in the different product distributions between the reactions in the gas phase and in the solution phase. The aliphatic cyclic imides and small cyclic ketones up to cycloheptanone undergo only the Norrish type I reaction from both singlet and triplet excited states, whereas acetophenone and benzophenone are often used as the Norrish type I photosensitizers. This reaction in the presence of zeolite and cyclodextrin and in the solid state produces good results. This reaction has been used extensively in organic synthesis and photochemistry.

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Polymeric Photoresist Nanoparticles: Light‐Induced Degradation of Hydrophobic Polymers in Aqueous Dispersion

Klinger

Landfester

2011

Macromol. Rapid Commun.

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Nanoparticles consisting of a photoreactive polymer able to radically switch its hydrophobicity are successfully prepared by miniemulsion polymerization. Irradiation with UV light causes degradation of the particles where at complete dissolution is achieved by changing the initial hydrophobic photoresist polymer into hydrophilic poly(methacrylic acid). Incorporation of the fluorescence-sensitive Nile red serves as a solvatochromic probe to study the particle degradation. Diffusion of either Nile red out from or water into the former hard spherical nanoparticles is studied and not only renders the described material an ideal system for applications, where in situ dissolution of nanoparticles may be needed, but also bears the additional advantage of performing controlled burst release.

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Electronic structure calculations of radical reactions for poly(methyl methacrylate) degradation

Cited by 34 publications

References 24 publications

Light-Sensitive Polymeric Nanoparticles Based on Photo-Cleavable Chromophores

Light-Sensitive Polymeric Nanoparticles Based on Photo-Cleavable Chromophores

Norrish Type I Reaction

Polymeric Photoresist Nanoparticles: Light‐Induced Degradation of Hydrophobic Polymers in Aqueous Dispersion

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