Fragmentation Chain Transfer Copolymerization Research Articles

Reversible addition fragmentation chain transfer copolymerization of functional myrcene with styrene

AbstractThe introduction of functionality is essential to the surface, bulk and mechanical properties of poly(diene‐styrene). In this work, copolymerizations of hydroxyl (My‐OH) and epoxide (My‐EPO) functionalized myrcenes with styrene by a solvent‐free reversible addition fragmentation chain transfer polymerization route have been performed. In both cases, the copolymerizations were processed with functional diene preferentially inserted (rMy‐OH/rSt, 1.28 ± 0.02/0.81 ± 0.02; rMy‐EPO/rSt, 1.15 ± 0.01/0.91 ± 0.02), providing a series of composition drifted copolymers with controlled functionality degree and molecular weight by feeding ratios of comonomer and chain transfer agent. The copolymers have remarkably low contact angles with water, an indication of potentially good miscibility with polar additives. In addition, the in‐chain included hydroxyl and epoxide groups could further provide a very versatile ‘intermediate’ that can be used to prepare various functional polymers, block and graft copolymers. © 2022 Society of Chemical Industry

Comprehensive studies of continuous flow reversible addition–fragmentation chain transfer copolymerization and its application for photoimaging materials

Thorough studies of RAFT copolymerization in a continuous flow to gain deeper insights into kinetics, reactivity, and applicability were conducted with monomers and solvents utilizable for chemically amplified resist systems.

Effects of alkyl group size on the structure and dynamics of poly(n-alkyl methacrylate)-based ionomers

The effects of alkyl group size on the structure and dynamics of poly(n-alkyl methacrylate)-based ionomers were investigated in this study. Ionomer samples were synthesized via the reversible addition–fragmentation chain transfer copolymerization of sodium styrene sulfonate and alkyl methacrylate with different alkyl groups (methyl, butyl, hexyl, lauryl, and octodecyl groups) and with varying ion contents. The samples were characterized by dielectric response spectroscopy (DRS), X-ray scattering, and linear viscoelasticity (LVE) measurements. X-ray scattering revealed ionic peaks indicative of spacing between ion aggregates. The interaggregate spacing decreased with increasing ion content when the alkyl groups were methyl, butyl, or hexyl groups. This observation is in accordance with the trend reported for sulfonated polystyrene, which has been extensively studied. In contrast, the interaggregate correlation peak merged with the backbone correlation peak when the alkyl groups were lauryl or octodecyl groups, suggesting that the steric repulsion of the long side chains partly suppressed the interchain association. Quantitative analysis of LVE showed that the sol-to-gel transition occurred at a higher number of ions per chain for samples with longer alkyl groups, lending support to the idea that long side chains generated increased steric repulsion. In addition, the plateau region broadened gradually with increasing alkyl group size, reflecting an increase in electrostatic interaction energy among the ionic groups. This increase was attributed to a reduction in the polarity of the polymer medium as the size of the nonpolar alkyl group increased, as detected by DRS.The effects of alkyl group size on the structure and dynamics of poly(n-alkyl methacrylate)-based ionomers were investigated in this study. Ionomer samples were synthesized via the reversible addition–fragmentation chain transfer copolymerization of sodium styrene sulfonate and alkyl methacrylate with different alkyl groups (methyl, butyl, hexyl, lauryl, and octodecyl groups) and with varying ion contents. The samples were characterized by dielectric response spectroscopy (DRS), X-ray scattering, and linear viscoelasticity (LVE) measurements. X-ray scattering revealed ionic peaks indicative of spacing between ion aggregates. The interaggregate spacing decreased with increasing ion content when the alkyl groups were methyl, butyl, or hexyl groups. This observation is in accordance with the trend reported for sulfonated polystyrene, which has been extensively studied. In contrast, the interaggregate correlation peak merged with the backbone correlation peak when the alkyl groups were lauryl or octodecyl gro...

Controlled synthesis of thermoresponsive polymers derived from l‐Lysine, a biorenewable resource

ABSTRACTRenewable lysine was cyclized to its corresponding α‐amino‐ε‐caprolactam and then underwent the reaction with acryloyl chloride to harvest a 2‐acrylamido‐caprolactam (ACL) monomer. Subsequent reversible addition–fragmentation chain transfer copolymerization of the obtained monomer with oligo(ethylene glycol)acrylate (OEGA) gave well‐defined P(ACL‐co‐OEGA) with low distribution. Nuclear magnetic resonance , size exclusion chromatography, and matrix‐assisted laser desorption ionization–time‐of‐flight–mass spectrometry measurements indicated the controlled feature of the polymerization. Moreover, the resultant copolymers demonstrated thermoresponsiveness, and the cloud points (Tcp) can be adjusted from 34 to 79 °C, by changing pH values, and the fraction of cyclic lysine. These results suggested that these lysine‐based thermoresponsive polymers might be used as new materials in biomedical fields. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 862–868

Starlike Branched Polyacrylamides by RAFT Polymerization-Part I: Synthesis and Characterization.

Starlike branched polyacrylamides (SB-PAMs) were synthesized using reversible addition–fragmentation chain transfer copolymerization of acrylamide (AM) and N,N′-methylenebis(acrylamide) (BisAM) in the presence of 3-(((benzylthio) carbonothioyl)thio)propanoic acid as a chain transfer agent, followed by chain extension with AM. The amount of incorporated BisAM in the core and the amount of AM during chain extension have been systematically varied. Core structures were achieved by incorporation of total monomer ratios [BisAM]/[AM] ranging from 0.010 to 0.143. The obtained macromolecular chain transfer agents had weight average molecular weights in the range of (2.2–7.8) × 103 Da and polydispersity indices between 1.2 and 15.1. Kinetic experiments were performed to investigate the extent of control of polymerization. Finally, the expansion of the core structures by chain-extension polymerization resulted in the successful preparation of high molecular weight SB-PAMs with apparent molecular weights ranging from 19 to 1250 kDa.

Stepwise Light-Induced Dual Compaction of Single-Chain Nanoparticles.

A photochemical strategy for the sequential dual compaction of single polymer chains is introduced. Two photoreactive methacrylates, with side chains bearing either a phenacyl sulfide (PS) or an α-methylbenzaldehyde (photoenol, PE) moiety, are selectively incorporated by one-pot iterative reversible-addition fragmentation chain transfer copolymerization into the outer blocks of a well-defined poly(methyl methacrylate) based ABC triblock copolymer possessing a nonfunctional spacer block (Mn = 23 400 g mol-1 , Đ = 1.2; ≈15 units of each photoreactive moieties of each type) as well as in model statistical copolymers bearing only one type of photoreactive unit. Upon UVA irradiation, PS and PE lead to highly reactive thioaldehydes and o-quinodimethanes, which rapidly react with dithiol and diacrylate linkers, respectively. The monomerfunctional copolymers are employed to establish the conditions for controlled intramolecular photo-crosslinking, which are subsequently applied to the bifunctional triblock copolymer. All compaction/folding experiments are monitored by size-exclusion chromatography and dynamic light scattering. The dual compaction consists of two events of dissimilar amplitude: the first folding step reveals a large reduction in hydrodynamic diameters, while the second compaction lead to a far less pronounced reduction of the single-chain nanoparticles size, consistent with the reduced degrees of freedom available after the first covalent compaction step.

Synthesis of PNVP-Based Copolymers with Tunable Thermosensitivity by Sequential Reversible Addition⁻Fragmentation Chain Transfer Copolymerization and Ring-Opening Polymerization.

Through the reversible addition–fragmentation chain transfer (RAFT) copolymerization of 3-ethyl-1-vinyl-2-pyrrolidone (C2NVP) and N-vinylpyrrolidone (NVP), a series of well-defined P(C2NVP-co-NVP) copolymers were synthesized (Mn = ca. 8000 to 16,000 and Mw/Mn <1.5) by using a difunctional chain transfer agent, S-(1-methyl-4-hydroxyethyl acetate) O-ethyl xanthate (MHEX). Copolymerizing kinetics and different monomer ratio in feeds were conducted to study the apparent monomer reaction rate and reactivity ratios of NVP and C2NVP, which indicated similar reaction rates and predominantly ideal random copolymers for the two monomers. The Tgs of the obtaining P(C2NVP-co-NVP) copolymers significantly corresponded to not only molecular weights MWs but also copolymer compositions. These copolymers presented characteristic lower critical solution temperatures (LCST) behavior. We then studied the cloud points (CPs) of the copolymers with varying MWs and compositions. With different MWs, the CPs were linearly decreased from ca. 51 to 45 °C. With different compositions, the CPs of the copolymers decreased from ca. 48 to 29 °C with C2NVP content (i.e., from 60.8 to 89.9 mol %). Fitting the CPs by the theoretical equation, the result illustrated that the introduction of more hydrophobic units of C2NVP suppressed the hydrophilic interaction between the polymer chain and water. We then successfully proceeded the chain extension through the ring-opening polymerization (ROP) of ε-caprolactone (CL) to the synthesis of a novel P(C2NVP-co-NVP)-b-PCL amphiphilic block copolymer (Mn,NMR = 14,730 and Mw/Mn = 1.59). The critical micelle concentration (CMC) of the block copolymer had a value of ca. 1.46 × 10−4 g/L. The block copolymer micelle was traced by dynamic light scattering (DLS), obtaining thermosensitive behaviors with a particle size of ca. 240 nm at 25 °C and ca. 140 nm at 55 °C, respectively.

Temperature and light-induced self-assembly changes of a tetra-arm diblock copolymer in an ionic liquid

A tetra-arm diblock copolymer ([PEG-b-P(AzoMA-r-NIPAm)]4) was synthesized by reversible addition–fragmentation chain transfer copolymerization of N-isopropylacrylamide (NIPAm) and 4-phenylazophenyl methacrylate (AzoMA), initiating from the ends of functionalized tetra-arm polyethylene glycol (tetra-PEG). The resulting tetra-arm diblock copolymer consists of two segments: tetra-PEG (the center block; compatible with 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim]PF6)) and P(AzoMA-r-NIPAm) (the end blocks; temperature- and photosensitive compatibility with [C4mim]PF6 due to photoresponsive upper critical solution temperature phase behavior). We found that [PEG-b-P(AzoMA-r-NIPAm)]4 underwent high-temperature unimer and low-temperature micelle (upper critical micellization temperature (UCMT)) transitions in [C4mim]PF6. The UCMT of the tetra-arm diblock copolymer depended on photoisomerization states of the azobenzene groups within the copolymer. The UCMT of the trans-form polymer in dark conditions was higher than that of the cis-form polymer under UV-light irradiation. We demonstrated photoinduced self-assembly changes of the tetra-arm diblock copolymer in [C4mim]PF6 at a ‘bistable’ temperature. Reversible photoinduced unimer/micelle transitions were also demonstrated. A tetra-arm diblock copolymer, consisting of tetra-PEG as central block and random copolymer of N-isopropylacrylamide (NIPAm) and 4-phenylazophenyl methacrylate (AzoMA) as four end blocks, exhibit high-temperature unimers and low-temperature micelles in a hydrophobic ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim]PF6). The upper critical micellization temperature depends on photoisomerization states of azobenzene in the copolymer. Photoinduced unimer/micelle transition was reversible at a suitable temperature.

Preparation and characterization of poly(styrene-alt-maleic acid)-b-polystyrene block copolymer self-assembled nanoparticles

Block copolymers poly(styrene-alt-maleic anhydride)-b-polystyrene (P(St-alt-MAn)-b-PSt) were synthesized via radical addition fragmentation chain transfer copolymerization. The maleic anhydride-containing segments of the block copolymer were hydrolyzed to form amphiphilic poly(styrene-alt-maleic acid)-b-polystyrene (P(St-alt-MA)-b-PSt). In aqueous solution, P(St-alt-MA)73-b-PSt81 and P(St-alt-MA)58-b-PSt130 formed stable dispersed spherical aggregates of approximately 25 and 40 nm, respectively. Particle size was stable under alkaline conditions and was little affected by the polymer concentration in the range of 0.025–1.0 mg mL−1. The critical aggregation concentrations of the block copolymer self-aggregates were 1 × 10−3 and 3 × 10−3 mg mL−1 for hydrophobic PSt block lengths of 130 and 81 monomer units, respectively. The nanoparticles had a negative surface charge at pH > 2. Scanning electron microscopy images revealed that particle–particle coalescence did not occur upon drying of the film and the nanoparticles remained discrete. Controlled aspirin release from the nanoparticles was dependent on the structure of the block polymers and release medium.

Tunable pH- and Temperature-Sensitive Copolymer Libraries by Reversible Addition−Fragmentation Chain Transfer Copolymerizations of Methacrylates

Reversible addition−fragmentation chain transfer (RAFT) polymerizations have been performed on a Chemspeed Accelerator SLT100 automated synthesizer to polymerize N,N-(dimethylamino)ethyl methacrylate (DMAEMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) at 70 °C. Azobis(isobutyronitrile) (AIBN) was used as source of radicals and 2-cyano-2-butyl dithiobenzoate (CBDB) as RAFT agent. A complete screening in composition of P(DMAEMA-stat-PEGMA) copolymers was elaborated from 0% of PEGMA to 100% of PEGMA. All polydispersity indices of the obtained copolymers are comprised between 1.11 and 1.30. The reactivity ratios have been determined by the extended Kelen−Tudos method (rDMAEMA = 0.93 and rPEGMA = 0.66). The behavior of the pH- and temperature-sensitive copolymers was studied in aqueous solution by measuring the lower critical solution temperature (LCST) by UV/vis spectroscopy. The measurements were performed at three different pH values (4, 7, and 10). At pH 7 and pH 10 it has been observed th...

Synthesis and Structural Analysis of Self-Associating Amphiphilic Statistical Copolymers in Aqueous Media

Amphiphilic statistical copolymer samples of sodium 2-(acrylamido)-2-methylpropanesulfonate and n-hexyl methacrylate with different degrees of polymerization and compositions were prepared by reversible addition−fragmentation chain transfer copolymerization, and their self-aggregating structure in 0.1 M aqueous NaCl was studied by light scattering, fluorescence, viscometry, and size exclusion chromatography. Major components of the copolymer samples were aggregates consisting of 2−7 polymer chains and possessing 1−5 hydrophobic microdomains, depending on the degree of polymerization and composition.

Reversible addition fragmentation chain transfer copolymerization: influence of the RAFT process on the copolymer composition

Reversible addition fragmentation chain transfer (RAFT) mediated and conventional copolymerizations at low monomer conversions have been carried out for the systems methyl methacrylate (MMA)-styrene, methyl acrylate (MA)-styrene and methyl methacrylate-butyl acrylate (BA). The polymer samples have been analyzed via 1H-NMR spectroscopy to obtain the copolymer composition and the terminal model reactivity ratios. In the RAFT mediated copolymerizations, the polymer mole fraction of the monomer with the larger reactivity ratio is increased compared to the conventional copolymerization. Simulations have been carried out using the program package PREDICI ® to examine possible explanations for the experimental findings. The simulations demonstrate that the RAFT process itself may alter the macroradical populations and the copolymer composition by offering additional reaction pathways. Further, the rate coefficients for the initiation reaction and the pre-equilibrium play an important role in determining the copolymer composition. The rate coefficients governing the main equilibrium of the RAFT process have only a minor impact on the copolymer composition.