Wavelength-Gated Photoreversible Polymerization and Topology Control

We exploit the wavelength dependence of [2+2] photocycloadditions and -reversions of styrylpyrene to exert unprecedented control over the photoreversible polymerization and topology of telechelic building blocks. Blue light affords high molar mass polymers that are stable at wavelengths exceeding 430 nm yet highly responsive to shorter wavelengths. UVB irradiation induces a rapid depolymerization yielding linear oligomers, whereas violet light generates cyclic entities. Different colors of light thus allow switching between a depolymerization that either proceeds through cyclic or linear topologies. The light-controlled topology formation was evidenced by correlation of mass spectrometry (MS) with size exclusion chromatography (SEC) and ion mobility data.<br>

Wavelength-Gated Photoreversible Polymerization and Topology Control

We exploit the wavelength dependence of [2+2] photocycloadditions and -reversions of styrylpyrene to exert unprecedented control over the photoreversible polymerization and topology of telechelic building blocks. Blue light affords high molar mass polymers that are stable at wavelengths exceeding 430 nm yet highly responsive to shorter wavelengths. UVB irradiation induces a rapid depolymerization yielding linear oligomers, whereas violet light generates cyclic entities. Different colors of light thus allow switching between a depolymerization that either proceeds through cyclic or linear topologies. The light-controlled topology formation was evidenced by correlation of mass spectrometry (MS) with size exclusion chromatography (SEC) and ion mobility data.<br>

Physics-Based Function Features for a Set of Material-Processing Verbs

Features are used in computer aided geometric modeling to encapsulate primitive and lower-abstraction entities to compose higher-level complex entities in order to support faster modeling, consistent data structures between features within the model, and feature-level reasoning that extends beyond reasoning supported by the primitives. In this paper, this idea is extended to computer-aided function modeling. Four function modeling features, which mainly operate on material flows but also involved energy flows, are formally defined. These features are: (1) Convergize_EM, (2) Handover_E, (3) Change_M, and (4) Changeover_EM. Each feature is composed of formerly established functional primitives that are formally defined, and by connecting those primitives in a controlled topology enforced by a feature-level grammar. The ability of these features to support consistent function modeling and model-based reasoning is illustrated using applications, both at the device level (simpler models) and at the system level (more complex models).

Construction of semi-fluorinated polyimides with perfluorocyclobutyl aryl ether-based side chains

This article reports the construction of PFCB aryl ether-based polyimides with precisely controlled topology via side-chain chemistry.