The synthesis of core-shell star copolymers via living free radical polymerization provides a convenient route to three-dimensional nanostructures having a poly(ethylene glycol) outer shell, a hydrophilic inner shell bearing reactive functional groups, and a central hydrophobic core. By starting with well-defined linear diblock copolymers, the thickness of each layer, overall size/molecular weight, and the number of internal reactive functional groups can be controlled accurately, permitting detailed structure/performance information to be obtained. Functionalization of these polymeric nanoparticles with a DOTA-ligand capable of chelating radioactive 64 Cu nuclei enabled the biodistribution and in vivo positron emission tomography (PET) imaging of these materials to be studied and correlated directly to the initial structure. Results indicate that nanoparticles with increasing PEG shell thickness show increased blood circulation and low accumulation in excretory organs, suggesting application as in vivo carriers for imaging, targeting, and therapeutic groups.

The synthesis of poly(methyl methacrylate-co-methacryloxysuccinimide-graft-poly(ethylene glycol)) (PMMA-co-PMASI-g-PEG) via living free radical polymerization provides a convenient route to well-defined amphiphilic graft copolymers having a controllable number of reactive functional groups, variable length PEG grafts, and low polydispersity. These copolymers were shown to form PMMA-core/PEG-shell nanoparticles upon hydrophobic collapse in water, with the hydrodynamic size being defined by the molecular weight of the backbone and the PEG grafts. Functionalization of these polymeric nanoparticles with a 1,4,7,10-tetraazacyclododecanetetraacetic acid (DOTA) ligand capable of chelating radioactive 64Cu nuclei enabled the biodistribution and in vivo positron emission tomography of these materials to be studied and directly correlated to the initial structure. Results indicate that nanoparticles with increasing PEG chain lengths show increased blood circulation and low accumulation in excretory organs, suggesting the possible use of these materials as stealth carriers for medical imaging and systemic administration.

Photosensitive polyimides (PSPIs) have been attracting great attention as insulating materials in microelectronic industry, and can be directly patterned to simplify processing steps. This article reviews recent works on development of PSPIs. After brief introduction, a typical PSPI formulation was described in comparison with a conventional method, followed by major strategies for the patterning. A number of recent reports on PSPIs were then divided into two major terms; positive-working and negative-working, and highlighted with focus on their chemistries up to pattern formation. In addition to the photosensitivity of PSPIs picked up in this review, other important subjects such as low-temperature imidization and low dielectric constants were also discussed.

A photosensitive semi-alicyclic poly(benzoxazole) based on poly(o-hydroxy amide) containing adamantyl units (PAHA) and 1,3,5-tris [(2-vinyloxy)ethoxy]benzene (TVEB) as an acidolytic de-crosslinker and a photoacid generator, diphenyliodonium 9,10-dimethoxyanthracene-2-sufonate (DIAS), has been developed. PAHA with a weight-average molecular weight of 24 100 was prepared from 1,3adamantanedicarbonyl chloride (ADC) and 4,4′-(hexafluoroisopropylidene)bis(o-aminophenol) (6FAP) in the presence of lithium chloride in N-methylpyrrolidinone (NMP) at 0 °C for 12 h. By thermal treatment, PAHA was easily converted to semi-alicyclic poly(benzoxazole) (PABO) that was insoluble in organic solvents and showed high thermal stability (T d5 ) 520 °C under N2). The UV-vis spectra of PAHA and PABO indicated excellent transparency at wavelengths above 320 and 400 nm, respectively. The average refractive index of PABO was 1.523, and the dielectric constant estimated from the refractive index was 2.55 at 1 MHz. This value is significantly lower than those of conventional wholly aromatic PBOs. The photosensitive PABO precursor, PAHA containing 15 wt % TVEB and 5 wt % DIAS, showed a sensitivity of 40 mJ/cm 2 and a contrast of 4.0 when it was exposed to a 365 nm light (i-line) and developed with a 2.38 wt % aqueous tetramethylammonium hydroxide solution (TMAHaq) at 25 °C. A fine positive image of 10 µm line-and-space pattern was also printed in a film which was exposed to 70 mJ/cm 2 of i-line by contact-printing mode. The positive image in PAHA was converted to the positive image in the PABO film by the thermal treatment without pattern deformation.