Synthesis, Thermodynamics, and Dynamics of Poly(4-tert-butylstyrene-b-methyl methacrylate)

Abstract

A series of symmetric poly(4-tert-butylstyreneblock-methyl methacrylate) (PtBS-b-PMMA) diblock copolymers with varying molar masses and narrow molar mass distributions were prepared using sequential anionic polymerization. Order-to-disorder transition (ODT) temperatures were determined as a function of the overall degree of polymerization, N, using a combination of low-frequency dynamic mechanical spectroscopy (DMS) and variable temperature small-angle X-ray scattering (SAXS), leading to a mean-field expression for the segment−segment interaction parameter, χ = (41.2 ± 0.9)/T − (0.044 ± 0.002). This material is characterized by a larger value of χ, and much greater temperature sensitivity, than polystyrene-b-PMMA, providing access to tunable lamellar periods (pitch) down to 14 nm at technologically relevant temperatures. Nucleation and growth of lamellae, following cooling from the disordered state, was characterized by SAXS well above the glass transition temperature (T g ≈ 130 °C) and extrapolated to lower processing temperatures based on polymer chain relaxation times extracted from time− temperature superposed DMS data. These results qualify PtBS-b-PMMA as an attractive candidate for development as a new lithographic material.

Control of polystyrene-block-poly(methyl methacrylate) directed self-assembly by laser-induced millisecond thermal annealing

“…[30][31][32] Based on our experimental measurement, the effective T ODT in directed regions appears to be between 650°C and 670°C. Self-assembly and registration to a directing pattern may require longer duration or multiple LSA anneals due to the small driving force directing pattern formation.…”

“…The often reported critical χN ODT ¼ 10.5 for phase segregation must be corrected for asymmetric BCP composition, finite chain length and fluctuation effects. 31,32 While these values neglect film thickness effects, 33 the correction is expected to be small relative to the large difference in reported χ values. Literature values for χ vary widely with some authors suggesting that the χ never falls below this critical χ ¼ 0.025 value for any temperature.…”

Revisiting the Anionic Polymerization of Methyl Ethacrylate

“…PMEA DP and volume fraction ( ƒ PMEA ) was determined using the block molar ratio, formula weight of the monomer repeat units, (FW S = 104.15, FW tBS = 160.26, and FW MEA = 114.14 g mol −1 ) and segment densities at 25 °C (ρ PS = 1.04, ρ PtBS = 0.94, and ρ PMEA = 1.18 g cm −3 ) . The volume corrected degree of polymerization, N , was determined using these density values and a reference volume, v 0 = 118 Å 3 . Low Ð values (≤1.15) were determined for each block polymer through SEC analysis (Figure S5, Supporting Information).…”

“…Using the same apparatus described above, sequential anionic block polymerization of PS‐PMEA or PtBS‐PMEA was performed by initiation of the styrenic block with s ‐BuLi, capping of the styrenic block with DPE, subsequent propagation of the MEA block, and termination of the polymerization with degassed methanol. A recently reported diblock polymerization of PtBS‐ block ‐poly(methyl methacrylate), (PtBS‐PMMA), provides this procedure in full detail; the only differences are the use of MEA instead of MMA and the length of time allowed for MEA to propagate.…”

Directed Self Assembly Materials for Semiconductor Lithography

“…25nm pitch. Simple modification of PS-b-PMMA, for example, poly(4-tert-butylstyrene-b-methyl methacrylate) (PtBS-b-PMMA) has χ-parameter 0.10 at 20°C, and this BCP can make 14nmP patterns [25], and other high χ-systems are described at following chapter.…”