Overview and status of the 0.5NA EUV microfield exposure tool at Berkeley Lab

A 0.5-NA extreme ultraviolet micro-field exposure tool has been installed and commissioned at beamline 12.0.1.4 of the Advanced Light Source synchrotron facility at Lawrence Berkeley National Laboratory. Commissioning has demonstrated a patterning resolution of 13 nm half-pitch with annular 0.35-0.55 illumination; a patterning resolution of 8 nm half-pitch with annular 0.1-0.2 illumination; critical dimension (CD) uniformity of 0.7 nm 1σ on 16 nm nominal CD across 80% of the 200 um x 30 um aberration corrected field of view; aerial image vibration relative to the wafer of 0.75 nn RMS and focus control and focus stepping better than 15 nm

RAFT aqueous dispersion polymerization yields poly(ethylene glycol)-based diblock copolymer nano-objects with predictable single phase morphologies

A poly(ethylene glycol) (PEG) macromolecular chain transfer agent (macro-CTA) is prepared in high yield (>95%) with 97% dithiobenzoate chain-end functionality in a three-step synthesis starting from a monohydroxy PEG113 precursor. This PEG113-dithiobenzoate is then used for the reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA). Polymerizations conducted under optimized conditions at 50 °C led to high conversions as judged by 1H NMR spectroscopy and relatively low diblock copolymer polydispersities (Mw/Mn < 1.25) as judged by GPC. The latter technique also indicated good blocking efficiencies, since there was minimal PEG113 macro-CTA contamination. Systematic variation of the mean degree of polymerization of the core-forming PHPMA block allowed PEG113-PHPMAx diblock copolymer spheres, worms, or vesicles to be prepared at up to 17.5% w/w solids, as judged by dynamic light scattering and transmission electron microscopy studies. Small-angle X-ray scattering (SAXS) analysis revealed that more exotic oligolamellar vesicles were observed at 20% w/w solids when targeting highly asymmetric diblock compositions. Detailed analysis of SAXS curves indicated that the mean number of membranes per oligolamellar vesicle is approximately three. A PEG 113-PHPMAx phase diagram was constructed to enable the reproducible targeting of pure phases, as opposed to mixed morphologies (e.g., spheres plus worms or worms plus vesicles). This new RAFT PISA formulation is expected to be important for the rational and efficient synthesis of a wide range of biocompatible, thermo-responsive PEGylated diblock copolymer nano-objects for various biomedical applications

RAFT polymerization of hydroxy-functional methacrylic monomers under heterogeneous conditions: effect of varying the core-forming block

Statistical copolymerization of a 1 : 1 molar ratio of a water-miscible monomer (2-hydroxyethyl methacrylate, HEMA) with a water-immiscible monomer (4-hydroxybutyl methacrylate, HBMA) has been conducted in water via reversible addition–fragmentation chain transfer (RAFT) polymerization using a water-soluble poly(glycerol monomethacrylate) macromolecular chain transfer agent (PGMA macro- CTA). In principle, such a hybrid formulation might be expected to be intermediate between RAFT dispersion polymerization and RAFT emulsion polymerization. Under such circumstances, it is of particular interest to examine whether both monomers are actually consumed and, if so, whether their rates of reaction are comparable. Given the water-solubility of both the PGMA macro-CTA and the free radical azo initiator, it is perhaps counter-intuitive that the water-immiscible HBMA is initially consumed significantly faster than the water-miscible HEMA, as judged by 1H NMR studies of this copolymerization. However, both comonomers are eventually almost fully consumed at 70 �C. A detailed phase diagram has been constructed for this RAFT formulation that enables reproducible syntheses of various pure copolymer morphologies, including spheres, worms and vesicles. It is emphasized that utilizing a 1 : 1 HEMA/HBMA molar ratio produces a core-forming statistical copolymer block that is isomeric with the poly(2-hydroxypropyl methacrylate) (PHPMA) core-forming block previously synthesized via RAFT aqueous dispersion polymerization (see A. Blanazs et al., Macromolecules, 2012, 45, 5099–5107). Hence it is rather remarkable that the thermo-responsive behavior of PGMA–P(HBMA-stat-HEMA) statistical block copolymer worm gels differs qualitatively from that exhibited by PGMA–PHPMA diblock copolymer worm gels

Synthesis of diblock copolymer nanoparticles via RAFT alcoholic dispersion polymerization: Effect of block copolymer composition, molecular weight, copolymer concentration, and solvent type on the final particle morphology

Various poly(2-hydroxyethyl methacrylate-b-benzyl methacrylate) (PHEMA n-PBzMAm) and poly(2-hydroxypropyl methacrylate-b-benzyl methacrylate) (PHPMAn-PBzMAm) nano-objects have been prepared via reversible addition-fragmentation chain transfer (RAFT) alcoholic dispersion polymerization. Using either a PHPMA or PHEMA macro-CTA as a steric stabilizer, chain extension with BzMA was conducted in methanol, ethanol, or isopropanol. In each case, in situ self-assembly is driven by the growing PBzMA chains, which become insoluble in lower alcohols above a certain critical chain length. Empirically, PHPMA macro-CTA proved to be much more effective than PHEMA macro-CTA in such syntheses, since the former conferred higher colloidal stability in alcohol. By constructing two detailed phase diagrams, the final nanoparticle morphology is shown to be sensitive to the DP of the core-forming block (PBzMA), the total solids content, and also the mean DP of the stabilizer block (PHPMA). The latter effect is readily demonstrated for PHPMA macro-CTAs possessing mean DPs of 48 and 63. Using PHPMA48 as a steric stabilizer, a range of nano-objects (spheres, worms or vesicles) can be accessed simply by tuning the DP of the core-forming PBzMA block. In contrast, using the PHPMA63 stabilizer only produces spherical morphologies. Presumably this is because the latter confers more effective steric stabilization, which prevents the efficient fusion of spheres to form worms. Nevertheless the PHPMA63-PBzMAn formulation may still be useful, since it allows access to spherical nanoparticles with tunable mean diameters of 29-100 nm. Such phase diagrams are essential for the reproducible targeting of copolymer morphologies, since they enable mixed phase regions to be avoided and allow the predictable synthesis of pure spheres, worms, or vesicles at a given concentration. Finally, a block copolymer "jellyfish" was observed during these PISA syntheses, which suggests that such intermediates are most likely a generic feature of the in situ conversion of worms into vesicles

Integration of a palliative care specialist in an amyotrophic lateral sclerosis clinic: Observations from one center

Palliative care specialists can aid in the care of patients with amyotrophic lateral sclerosis (ALS). In this article, we describe our 1-year experience incorporating a palliative care specialist into the ALS multidisciplinary team. We describe our integration model, patient selection, and visit content. Of 500 total clinic patients, 74 (14.8%) were seen by the palliative care specialist in 1 year. Referral was most often triggered by advance care planning needs (91%). In the initial visit with the palliative care specialist, topics most frequently covered included goals of care (84%), anxiety/depression (35%), and medical decision-making about feeding tubes (27%) or tracheostomy (31%). Symptom management comprised a relatively small number of the visits, and duration of visits was limited by patient fatigue. Patients with complex goals of care may benefit from the input of a palliative care specialist, and unique integration models may help to facilitate care delivery. Muscle Nerve 60: 137-140, 2019

Integration of a palliative care specialist in an amyotrophic lateral sclerosis clinic: Observations from one center

Palliative care specialists can aid in the care of patients with amyotrophic lateral sclerosis (ALS). In this article, we describe our 1-year experience incorporating a palliative care specialist into the ALS multidisciplinary team. We describe our integration model, patient selection, and visit content. Of 500 total clinic patients, 74 (14.8%) were seen by the palliative care specialist in 1 year. Referral was most often triggered by advance care planning needs (91%). In the initial visit with the palliative care specialist, topics most frequently covered included goals of care (84%), anxiety/depression (35%), and medical decision-making about feeding tubes (27%) or tracheostomy (31%). Symptom management comprised a relatively small number of the visits, and duration of visits was limited by patient fatigue. Patients with complex goals of care may benefit from the input of a palliative care specialist, and unique integration models may help to facilitate care delivery. Muscle Nerve 60: 137-140, 2019

Universal polymer analysis by 1H NMR using complementary trimethylsilyl end groups

New degenerative chain transfer agents, namely 4-(trimethylsilyl)benzyl 4-(trimethylsilyl)butane-dithioate, 4-(trimethylsilyl)benzyl 3-(trimethylsilyl)propyl trithiocarbonate and their 3-(trimethylsilyl)benzyl isomers, that are two-fold labeled with complementary trimethylsilyl (TMS) markers, were designed and shown to be powerful tools for universal polymer analysis by conventional 1H NMR spectroscopy. Their use in controlled free radical polymerization, here the reversible addition-fragmentation chain transfer (RAFT) method, resulted in polymers with low polydispersities up to high molar masses, as well as with defined complementary TMS end groups. Thus, routine 1H NMR spectra allowed facile determination of the molar masses of polymers of various chemical structures up to at least 105 g/mol, and simultaneously provided crucial information about the content of end groups that is typically >95% when polymerizations are correctly performed. Polymerizations were carried out in various solvents for two standard monomers, namely n-butyl acrylate and styrene, as well as for two specialty monomers, so-called inimers, namely 2-(2-chloropropionyloxy)ethyl acrylate and 2-(2-chloropropionyloxy)ethyl acrylamide. The complementary end group markers revealed marked differences in the suitability of commonly used solvents for RAFT polymerization. The results demonstrate—beyond good polymerization control—that the new RAFT agents are universal, powerful tools for facile polymer analysis by routine 1H NMR spectroscopy, of their absolute molar masses as well as of the content of end groups. This is crucial information, e.g., for the synthesis of high-quality telechelics and, in particular, of block copolymers, which is difficult to obtain by other methods. Preliminary screening experiments indicate that similar uses can be envisaged for analogous ATRP systems

Synthesis of Diblock Copolymer Nanoparticles via RAFT Alcoholic Dispersion Polymerization: Effect of Block Copolymer Composition, Molecular Weight, Copolymer Concentration, and Solvent Type on the Final Particle Morphology

Various poly­(2-hydroxyethyl methacrylate-<i>b</i>-benzyl methacrylate) (PHEMA_<i>n</i>–PBzMA_<i>m</i>) and poly­(2-hydroxypropyl methacrylate-<i>b</i>-benzyl methacrylate) (PHPMA_<i>n</i>–PBzMA_<i>m</i>) nano-objects have been prepared via reversible addition–fragmentation chain transfer (RAFT) alcoholic dispersion polymerization. Using either a PHPMA or PHEMA macro-CTA as a steric stabilizer, chain extension with BzMA was conducted in methanol, ethanol, or isopropanol. In each case, <i>in situ</i> self-assembly is driven by the growing PBzMA chains, which become insoluble in lower alcohols above a certain critical chain length. Empirically, PHPMA macro-CTA proved to be much more effective than PHEMA macro-CTA in such syntheses, since the former conferred higher colloidal stability in alcohol. By constructing two detailed phase diagrams, the final nanoparticle morphology is shown to be sensitive to the DP of the core-forming block (PBzMA), the total solids content, <i>and also the mean DP of the stabilizer block</i> (PHPMA). The latter effect is readily demonstrated for PHPMA macro-CTAs possessing mean DPs of 48 and 63. Using PHPMA₄₈ as a steric stabilizer, a range of nano-objects (spheres, worms or vesicles) can be accessed simply by tuning the DP of the core-forming PBzMA block. In contrast, using the PHPMA₆₃ stabilizer only produces spherical morphologies. Presumably this is because the latter confers more effective steric stabilization, which prevents the efficient fusion of spheres to form worms. Nevertheless the PHPMA₆₃–PBzMA_<i>n</i> formulation may still be useful, since it allows access to spherical nanoparticles with tunable mean diameters of 29–100 nm. Such phase diagrams are essential for the reproducible targeting of copolymer morphologies, since they enable mixed phase regions to be avoided and allow the predictable synthesis of pure spheres, worms, or vesicles at a given concentration. Finally, a block copolymer “jellyfish” was observed during these PISA syntheses, which suggests that such intermediates are most likely a <i>generic</i> feature of the <i>in situ</i> conversion of worms into vesicles