RESUMO
In order to move away from traditional petrochemical-based polymer materials, it is imperative that new monomer systems be sought out based on renewable resources. In this work, the synthesis of a functional terpene-containing acrylate monomer (tetrahydrogeraniol acrylate, THGA) is reported. This monomer was polymerized in toluene and bulk via free-radical polymerizations, achieving high conversion and molecular weights up to 278 kg·mol-1. The synthesized poly(THGA) shows a relatively low Tg (-46 °C), making it useful as a replacement for low Tg acrylic monomers, such as the widely used n-butyl acrylate. RAFT polymerization in toluene ([M]0 = 3.6 mol·L-1) allowed for the well-controlled polymerization of THGA with degrees of polymerization (DP n) from 25 to 500, achieving narrow molecular weight distributions ( D̵ ≈ 1.2) even up to high conversions. At lower monomer concentrations ([M]0 = 1.8 mol·L-1), some evidence of intramolecular chain transfer to polymer was seen by the detection of branching (arising from propagation of midchain radicals) and terminal double bonds (arising from ß-scission of midchain radicals). Poly(THGA) was subsequently utilized for the synthesis of poly(THGA)- b-poly(styrene)- b-poly(THGA) and poly(styrene)- b-poly(THGA)- b-poly(styrene) triblock copolymers, demonstrating its potential as a component of thermoplastic elastomers. The phase separation and mechanical properties of the resulting triblock copolymer were studied by atomic force microscopy and rheology.
Assuntos
Acrilatos/química , Elastômeros , Polimerização , Terpenos/química , Elastômeros/síntese química , Elastômeros/químicaRESUMO
The controlled synthesis of poly(oligo(2-ethyl-2-oxazoline)methacrylate) (P(OEtOxMA)) polymers by Cu(0)-mediated polymerization in water/methanol mixtures is reported. Utilizing an acetal protected aldehyde initiator for the polymerization, well-defined polymers are synthesized (>99% conversion, Ð < 1.25) with subsequent postpolymerization deprotection resulting in α-aldehyde end group containing comb polymers. These P(OEtOxMA) are subsequently site-specifically conjugated, via reductive amination, to a dipeptide (NH2 -Gly-Tyr-COOH) as a model peptide, prior to conjugation to the functional peptide oxytocin. The resulting oxytocin conjugates are evaluated in comparison to poly(oligo(ethylene glycol) methyl ether methacrylate) combs synthesized in the same manner for potential effects on thermal stability in comparison to the native peptide.
Assuntos
Aminas/síntese química , Cobre/química , Peptídeos/química , Polimerização , Ácidos Polimetacrílicos/química , Água/química , Aminação , Aminas/química , Metanol/química , Estrutura MolecularRESUMO
The synthesis of hydrophilic, thermoresponsive, and zwitterionic polymethacrylates is reported by Cu(0)-mediated reversible deactivation radical polymerization in water and/or water/alcohol mixtures. The predisproportionation of [Cu(I) (PMDETA)Cl] in water prior to initiator and monomer addition is exploited to yield well-defined polymethacrylates with full monomer conversions in 30 min. The addition of supplementary halide salts (NaCl) enables the synthesis of various molecular weight poly[poly(ethylene glycol) methyl ether methacrylate] (PEGMA475) (DPn = 10-80, Mn ≈ 10,000-40 000 g mol(-1)) with full monomer conversion and narrow molecular weight distributions attained in all cases (D ≈ 1.20-1.30). A bifunctional PEG initiator (average Mn ≈ 1000 g mol(-1)) is utilized for the polymerization of a wide range of methacrylates including 2-dimethylaminoethyl methacrylate, 2-morpholinoethyl methacrylate, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, and 2-methacryloyloxyethyl phosphorylcholine. Despite the high water content, high end group fidelity is demonstrated by in situ chain extensions and block copolymerizations with PEGMA475 yielding well-defined functional telechelic pentablock copolymers within 2.5 h.
Assuntos
Polímeros/síntese química , Etilaminas/síntese química , Etilaminas/química , Temperatura Alta , Interações Hidrofóbicas e Hidrofílicas , Metacrilatos/síntese química , Metacrilatos/química , Estrutura Molecular , Peso Molecular , Polietilenoglicóis/síntese química , Polietilenoglicóis/química , Polimerização , Polímeros/químicaRESUMO
The polymerisation of N-acryloylmorpholine in water is reported utilising Cu(0)-mediated living radical polymerisation (SET-LRP). The inherent instability of [Cu(I) (Me6-Tren)Br] in aqueous solution is exploited via rapid disproportionation to prepare Cu(0) particles and [Cu(II) (Me6-Tren)Br2 ] in situ prior to addition of monomer and initiator. Quantitative conversion is attained within 30 min for various degrees of polymerisation (DPn = 20-640) with SEC showing symmetrical narrow molecular weight distributions (D < 1.18) in all cases. Optimised conditions are subsequently applied for the preparation of a diblock copolymer poly(NIPAm)-b-(N-acryloylmorpholine), illustrating the versatility of this approach.
Assuntos
Cobre/química , Radicais Livres/química , Morfolinas/química , Polímeros/química , Água/química , Materiais Biocompatíveis/síntese química , Materiais Biocompatíveis/química , Interações Hidrofóbicas e Hidrofílicas , Polimerização , Polímeros/síntese químicaRESUMO
Despite significant efforts, the design of alkoxyamines for polymerization of methacrylic monomers in a well-controlled fashion with good retention of the active chain ends remains a challenge. Herein, the facile synthesis of several alkoxyamines, which are capable of achieving this long sought-after goal, is reported. Controlled homopolymerization of methyl methacrylate is achieved as determined by a linear increase in molecular weight with conversion and first-order rate plots for various alkoxyamine concentrations. The versatility of the alkoxyamines is further exemplified by the ability to control the homopolymerization of styrene and by synthesis of a block copolymer of a second methacrylate in an efficient chain extension process.
RESUMO
Polymerization-induced self-assembly (PISA) is a versatile technique to achieve a wide range of polymeric nanoparticle morphologies. Most previous examples of self-assembled soft nanoparticle synthesis by PISA rely on a growing solvophobic polymer block that leads to changes in nanoparticle architecture during polymerization in a selective solvent. However, synthesis of block copolymers with a growing stimuli-responsive block to form various nanoparticle shapes has yet to be reported. This new concept using thermoresponsive polymers is termed polymerization-induced thermal self-assembly (PITSA). A reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide from a hydrophilic chain transfer agent composed of N,N-dimethylacrylamide and acrylic acid was carried out in water above the known lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNIPAm). After reaching a certain chain length, the growing PNIPAm self-assembled, as induced by the LCST, into block copolymer aggregates within which dispersion polymerization continued. To characterize the nanoparticles at ambient temperatures without their dissolution, the particles were crosslinked immediately following polymerization at elevated temperatures via the reaction of the acid groups with a diamine in the presence of a carbodiimide. Size exclusion chromatography was used to evaluate the unimer molecular weight distributions and reaction kinetics. Dynamic light scattering and transmission electron microscopy provided insight into the size and morphologies of the nanoparticles. The resulting block copolymers formed polymeric nanoparticles with a range of morphologies (e.g., micelles, worms, and vesicles), which were a function of the PNIPAm block length.