There are no reports of star polymers synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization in aqueous dispersions (e.g. emulsion, miniemulsions). In this work, we used two RAFT agents to produce linear and 4-arm star polymers in a well-controlled miniemulsion system using conventional surfactants (sodium dodecyl sulfate and hexadecane) and initiators (ammonium persulfate). The miniemulsions were formed through ultrasonication of the polymerization mixture to produce very small droplet sizes. Polymerization of styrene in these miniemulsions resulted in the formation of polymer nanoparticles of approximately 60 and 75 nm with narrow particle size distributions regardless of the targeted molecular weight. The rate of polymerization in these miniemulsions (100% conversion after 3.3 h) was significantly faster than in solution (60% conversion after 20 h). The reason for this fast rate was due to compartmentalization of the radicals within the growing particles. In addition, narrow MWDs were produced with polydispersity (PDIMWD) values below 1.22 for the linear and below 1.09 for the 4-arm star polymers. The particle size distributions were found to be narrow, less than 0.055 for the linear and less than 0.113 for the 4-arm star polymers. This is the first successful miniemulsion, to our knowledge, of 4-arm stars by RAFT to create both narrow molecular weight and narrow particle size distributions. The properties of such polymer latex particles are yet to be explored but they should have vastly different properties compared to latex particles with linear polymers. Our work opens a synthetic route to this class of latex particles previously unobtainable using conventional reagents, and providing exciting opportunities for various applications.
Out of band (OOB) radiation from the EUV source has significant implications for the performance of EUVL photoresists. Here we introduce a surface-active polymer additive, capable of partitioning to the top of the resist film during casting and annealing, to protect the underlying photoresist from OOB radiation. Copolymers were prepared using reversible addition-fragmentation chain transfer (RAFT) polymerization, and rendered surface active by chain extension with a block of fluoro-monomer. Films were prepared from the EUV resist with added surface-active Embedded Barrier Layer (EBL), and characterized using measurements of contact angles and spectroscopic ellipsometry. Finally, the lithographic performance of the resist containing the EBL was evaluated using Electron Beam Lithography exposure
Iodine transfer polymerization (ITP) of vinylidene fluoride (VDF) in the presence of two chain transfer agents (CTA, such as C6F13I and HC2F4CH2I) is presented. Various experimental conditions in terms of the nature of the radical initiators, time, temperature and initial [initiator]0/[VDF]0 and [CTA]0/[VDF]0 molar ratios influenced the yield of the reaction, the obtained average degree of polymerization in number, n, of PVDF−I, the defect of VDF-chaining, and the CX2I functionality (where X = H or F). The microstructures of these produced PVDF−I oligomers were characterized by 1H and 19F NMR spectroscopy which enabled one to assess the n values and to quantify the head-to-head or tail-to-tail defects of VDF-chainings. A low amount of defect of chaining in PVDF−I when C6F13I was used in contrast to a higher content from HC2F4CH2I. These PVDF−Is exhibited a favored −CH2CF2I functionality from the former CTA which was not observed in the latter one. A good agreement between the targeted and the obtained n values was noted for ITP of VDF in the presence of C6F13I (representative of normal addition) whereas that carried out from HC2F4CH2I (representative of inverse addition) led to experimental n values higher than the targeted ones in all cases. A low conversion of HC2F4CH2I was observed in contrast to that of C6F13I, which shows a better efficiency as the transfer agent.
Carrying out organic reactions in water-based nanoreactors represents a ‘green’ method for the preparation of organic compounds. This process eliminates the need for solvents, thus reducing the effect of high volumes of solvent on the environment. In this work, we demonstrate a successful Heck cross-coupling reaction, one of the most used approaches to form C–C bonds using a palladium catalyst, in a miniemulsion. The miniemulsion droplet sizes were small (25 to 42 nm), and the reactions resulted in high conversions of three different products with high trans stereoisomers.
Bilayer polymer thin films, that form through the surface segregation of a surface-active component, provide the ability to tailor interfacial properties and are relevant to many technological applications, including photolithography. For example, polymers with fluorine-containing end groups will selectively accumulate at the polymer–air interface when the second polymer is not fluorinated, but what happens when both polymers in a bilayer film are fluorinated? To test this, we prepared polymers via reversible addition–fragmentation chain transfer (RAFT) polymerization, which were then end group modified with a fluorine-containing small molecule or by chain extension with a fluorinated monomer to form a short fluorine-containing block. These partially fluorinated polymers were then blended with an extreme ultraviolet (EUV) photoresist that had a degree of in-chain fluorination, and thin films of the blends were prepared. To probe multilayer formation and assess the competition of the end group modified, fluoro-block, and in-chain fluorinated groups for the polymer–air interface, the films were characterized using contact angle measurements and static time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results reveal important insights into the effect of fluoro-block length on directing self-segregation of the polymeric additive. The effect of the addition of the low surface energy polymer on the lithographic performance of the photoresist was confirmed using electron beam lithography.
'/%3e%3c/defs%3e%3cpath fill='%23012169' d='M0 0h10080v5040H0z'/%3e%3cpath stroke='%23fff' stroke-width='.6' d='m0 0 6 3m0-3L0 3' clip-path='url(%23b)' transform='scale(840)'/%3e%3cpath stroke='%23e4002b' stroke-width='.4' d='m0 0 6 3m0-3L0 3' clip-path='url(%23c)' transform='scale(840)'/%3e%3cpath stroke='%23fff' stroke-width='840' d='M2520 0v2520M0 1260h5040'/%3e%3cpath stroke='%23e4002b' stroke-width='504' d='M2520 0v2520M0 1260h5040'/%3e%3cg fill='%23fff'%3e%3cuse xlink:href='%23d' x='2520' y='3780'/%3e%3cuse xlink:href='%23a' x='7560' y='4200'/%3e%3cuse xlink:href='%23a' x='6300' y='2205'/%3e%3cuse xlink:href='%23a' x='7560' y='840'/%3e%3cuse xlink:href='%23a' x='8680' y='1869'/%3e%3cuse xlink:href='%23e' x='8064' y='2730'/%3e%3c/g%3e%3c/svg%3e)
