Daniel J. Arriola

Crosslinker reactivity and the structure of superabsorbent gels

A 13C-labeled crosslinker (trimethylolpropane triacrylate, TMPTA) was synthesized and copolymerized with acrylic acid while monitoring the relative rates of reaction of the crosslinker and acrylic acid by 13C-NMR. This allowed easy quantification of the concentration of the minor component (crosslinker) in the polymer and monomer mixture to levels as low as 0.02%. Polymerizations were conducted in 5 mm NMR tubes under varied temperature, percent neutralization (pH), and percent solids. Reactivity ratios were determined from the rates of incorporation of the components into the gel by use of the integrated form of the copolymerization equation, and their sensitivity to the above variables was quantified. The relative rate of incorporation of the crosslinker into the gel was exceedingly fast. The reactivity ratio, r1 for acrylic acid, varied from 0.31 (65% neutralization) to 0.77 (unneutralized). The reactivity ratio was affected by the percent solids (solvent effect), but was insensitive to temperature over the range of 55–80°C. It was observed that all of the double bonds of TMPTA were incorporated into gel network as opposed to prior models predicting only two bonds reacting. The reported inefficiency of TMPTA is postulated to be caused by a solubility problem in the monomer mixture. Very low levels of extractables were found in the products even though the crosslinker was consumed by 70% conversion. Based on these data, we propose that a major component of the gel network is graft polymer that forms late in the polymerization onto the crosslinked gel formed earlier.

Chain Shuttling Catalysis and Olefin Block Copolymers (OBCs)

Olefin block copolymers (OBCs) with new-to-the-world properties have recently been made via a process called chain shuttling polymerization. These systems comprise two or more catalysts with differing affinities for comonomer combined with a chain shuttling agent (CSA), which distributes the growing polymer chains among the various catalysts. The result is a unique block copolymer, with statistically distributed block sizes and numbers of blocks per chain. A unique property of the materials is that the melting temperature is nearly independent of the comonomer incorporation, which breaks a seemingly immutable relationship that was long held to be true.

Impact of polymerization process on OOB on lithographic performance of a EUV resist

Several approaches have been used to minimize LWR in advanced resists. Various polymer and matrix properties, such as polymer molecular volume and free volume fraction, polymer dissolution, impact of activation energy of the deprotection reaction and distribution of small molecules in the polymer matrix have been shown to influence the functional behavior of the resist. We have developed polymerization methods to improve the incorporation and homogeneity of monomers, including PAG monomer, in an EUV resist polymer. Further, we report on use of a new cation which imparts reduced OOB character and a 30% improvement in LWR for a 28nm L/S feature with sensitivity of 10mJ/cm2 versus a control containing the TPS cation. Additionally this new material is capable of 21nm resolution. We also tested the new cation for outgassing by RGA and observed a 60% reduction in outgassing versus a TPS control.