For the first time, ATRP was successfully employed for homopolymerization of a commercial methacrylate-functionalized polyhedral oligomeric silsesquioxane (POSS) monomer, iBuPOSSMA, to high molecular ...weights. It was found that iBuPOSSMA has a low ceiling temperature (T c); therefore, low temperatures and/or high initial monomer concentrations need to be used in order to avoid low degrees of polymerization that had been observed previously. The values of T c, as well as of the polymerization enthalpy ΔH p and entropy ΔS p were determined to be 130 °C (at M0 = 1 M), −41 kJ mol–1, and −101 J mol–1 K–1, respectively. Under optimized conditions, poly(iBuPOSSMA) homopolymers having low dispersity and high M n, ranging from 23 000 to 460 000, were obtained in a well-controlled ATRP process. Moreover, various block copolymers having high-M n poly(iBuPOSSMA) blocks were prepared by copolymerization of iBuPOSSMA with methyl methacrylate and styrene.
Temperature behavior of D2O solutions of poly(ethylene oxide) (PEO)114‐block‐poly(N‐isopropylacrylamide) (PNIPAm)109 is characterized by NMR methods. At temperatures above the lower critical solution ...temperature (LCST) transition of PNIPAm component, 1H NMR spectra are consistent with existence of micelles where immobilized PNIPAm blocks form rather compact core and mobile PEO blocks form a shell of micelles. The transition of PNIPAm component shifts toward lower temperatures with increasing polymer concentration. 2D nuclear Overhauser effect spectroscopy spectra which can provide information on proton groups in close spatial contact (<0.5 nm) show an increase in intensity of cross‐peaks between PEO protons and main chain CH and CH2 protons, and isopropyl CH protons of PNIPAm units after increasing the temperature from 292.7 to 301.6 K. The fact that this change occurs at temperature, which is still below the LCST transition of PNIPAm component evidences certain conformation changes in the PEO‐b‐PNIPAm block copolymer already in the pretransition region.
Temperature behavior of D2O solutions of poly(ethylene oxide)114‐block‐poly(N‐isopropylacrylamide) (PNIPAm)109 block copolymer, which forms micelles at temperatures above the lower critical solution temperature transition of PNIPAm component, is characterized by NMR methods. Analysis of temperature dependences of 2D 1H–1H nuclear Overhauser effect spectroscopy spectra evidences conformation changes in the block copolymer already in the pretransition region.
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•A library of sulfonated polystyrenes differing in MW and polarity was synthesized.•Polymers effective in solubilizing model cell membranes were identified.•The lead polymer forms ...stable particles (nanodiscs) from model DMPC liposomes.•Polymers remain soluble at low pH and in the presence of Mg2+ ions.
Amphiphilic polymers are increasingly applied in the detergent-free isolation and functional studies of membrane proteins. However, the carboxylate group present in the structure of many popular variants, such as styrene-maleic acid (SMA) copolymers, brings limitations in terms of polymer sensitivity to precipitation at acidic pH or in the presence of divalent metal cations. Herein, we addressed this problem by replacing carboxylate with the more acidic sulfonate groups. To this end, we synthesized a library of amphiphilic polystyrene-co-(sodium 4-styrene sulfonate) copolymers (termed SSS), differing in their molecular weight and overall polarity. Using model cell membranes (Jurkat), we identified two copolymer compositions (SSS-L30 and SSS-L36) that solubilized membranes to an extent similar to SMA. Interestingly, the density gradient ultracentrifugation/SDS-PAGE/Western blotting analysis of cell lysates revealed a distribution of studied membrane proteins in the gradient fractions that was different than for SMA-solubilized membranes. Importantly, unlike SMA, the SSS copolymers remained soluble at low pH and in the presence of Mg2+ ions. Additionally, the solubilization of DMPC liposomes by the lead materials was studied by turbidimetry, DLS, SEC, and high-resolution NMR, revealing, for SSS-L36, the formation of stable particles (nanodiscs), facilitated by the direct hydrophobic interaction of the copolymer phenyls with lipid acyl chains.
Controlled synthesis of high‐molecular weight (MW) organic–inorganic hybrid polymers based on polyhedral oligomeric silsesquioxane (POSS) monomers has previously proved difficult to achieve by ...reversible‐deactivation radical polymerization methods. Here, this problem is tackled by employing a rarely used combination of Cu(0) catalysis and nonpolar solvents to polymerize a POSS‐methacrylate monomer,
i
BuPOSSMA. It is revealed that chain transfer to solvent plays a dominant role in this system as only benzene and not toluene allows for synthesis of low dispersity, ultrahigh MW products (up to 3 500 000). Importantly, the process is characterized by very low amounts (units of ppm) of copper released into the polymerization mixture, leading to products with no discoloration. Finally, benzene use is also shown to be beneficial for copper bromide–catalyzed polymerization of
i
BuPOSSMA, affording polymers with moderate MWs and extremely low dispersities (down to 1.06).
Ultrahigh molecular weight (MW) polypolyhedral oligomeric silsesquioxane (POSS)‐methacrylates are accessible via a niche method, copper‐catalyzed reversible‐deactivation radical polymerization in nonpolar media. Chain transfer to solvent is the main detrimental factor here. Only in benzene as a low transferring solvent, low‐dispersity, and high‐MW products are achieved. Atom transfer radical polymerization of POSS‐methacrylate in benzene then provides poly(POSS‐methacrylates) of extremely low dispersity.
Low‐molecular weight (MW) amphiphilic copolymers have been recently introduced as a powerful tool for the detergent‐free isolation of cell membrane proteins. Herein, a screening approach is used to ...identify a new copolymer type for this application. Via a two‐step ATRP/acidolysis procedure, a 3 × 3 matrix of well‐defined poly(butyl methacrylate)‐co‐(methacrylic acid) copolymers (denoted BMAA) differing in their MW and ratio of hydrophobic (BMA) and hydrophilic (MAA) units is prepared. Subsequently, using the biologically relevant model (T‐cell line Jurkat), two compositions of BMAA copolymers are identified that solubilize cell membranes to an extent comparable to the industry standard, styrene‐maleic acid copolymer (SMA), while avoiding the potentially problematic phenyl groups. Surprisingly, while only the lowest‐MW variant of the BMA/MAA 2:1 composition is effective, all the copolymers of the BMA/MAA 1:1 composition are found to solubilize the model membranes, including the high‐MW variant (MW of 14 000). Importantly, the density gradient ultracentrifugation/sodium dodecyl sulfate‐polyacrylamide gel electrophoresis/Western blotting experiments reveal that the BMA/MAA 1:1 copolymers disintegrate the Jurkat membranes differently than SMA, as demonstrated by the different distribution patterns of two tested membrane protein markers. This makes the BMAA copolymers a useful tool for studies on membrane microdomains differing in their composition and resistance to membrane‐disintegrating polymers.
Well‐defined amphiphilic copolymers of butyl methacrylate and methacrylic acid (BMAA) with tailored molecular weight and overall polarity are demonstrated to be effective in the solubilization of membrane proteins. Some of the BMAA variants disintegrate the model Jurkat membranes differently than the industry standard (styrene/maleic acid copolymers), which makes them useful tools for studies on specific types of membrane microdomains.
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•We studied thermoresponsive block copolymers PEO-b-PNIPAm and PEO-b-(PNIPAm)2 in D2O.•We used a combination of NMR, FTIR, DSC and quantum-chemical calculations.•Thermoresponsive ...behavior is affected by the PEO block and copolymer architecture.•A portion of water bound in copolymer micellar cores was established by NMR and FTIR.•Dehydration of PNIPAm segments is higher in block copolymers than in homopolymer.
Temperature behavior of D2O solutions of thermoresponsive diblock poly(ethylene oxide) (PEO)-b-poly(N-isopropylacrylamide) (PNIPAm) copolymers and Y-shape triblock PEO-b-(PNIPAm)2 copolymers was investigated and compared with the phase transition of the PNIPAm homopolymer by combination of NMR and ATR FTIR spectroscopy, DSC and model quantum-chemical calculations. It is shown that the phase transition and structures of PNIPAm component (forming micellar cores) are significantly affected not only by the presence of the PEO block but also by copolymer architecture. Both these factors affect energetics of the phase transition, influence of the polymer concentration and behavior of bound water at elevated temperatures. They also affect the degree of dehydration of PNIPAm segments (CO groups) at temperatures above the phase transition which is higher for block copolymers (especially for the diblock) in comparison with PNIPAm homopolymer. NOESY NMR spectra likewise revealed influence of the architecture of the block copolymer on its conformational behavior in the pretransition region.
Amphiphilic polymers are increasingly applied in the detergent-free isolation and functional studies of membrane proteins. However, the carboxylate group present in the structure of many popular ...variants, such as styrene-maleic acid (SMA) copolymers, brings limitations in terms of polymer sensitivity to precipitation at acidic pH or in the presence of divalent metal cations. Herein, we addressed this problem by replacing carboxylate with the more acidic sulfonate groups. To this end, we synthesized a library of amphiphilic polystyrene-
-(sodium 4-styrene sulfonate) copolymers (termed SSS), differing in their molecular weight and overall polarity. Using model cell membranes (Jurkat), we identified two copolymer compositions (SSS-L30 and SSS-L36) that solubilized membranes to an extent similar to SMA. Interestingly, the density gradient ultracentrifugation/SDS-PAGE/Western blotting analysis of cell lysates revealed a distribution of studied membrane proteins in the gradient fractions that was different than for SMA-solubilized membranes. Importantly, unlike SMA, the SSS copolymers remained soluble at low pH and in the presence of Mg
ions. Additionally, the solubilization of DMPC liposomes by the lead materials was studied by turbidimetry, DLS, SEC, and high-resolution NMR, revealing, for SSS-L36, the formation of stable particles (nanodiscs), facilitated by the direct hydrophobic interaction of the copolymer phenyls with lipid acyl chains.
Low‐molecular weight (MW) solvent‐borne functional (meth)acrylic polymers find an important use in coating resins. However, when preparing such polymers through copper‐mediated ...reversible‐deactivation radical polymerization (RDRP), contamination with colored copper species and the use of expensive ligands represent significant obstacles from the industrial application viewpoint. Here, we investigated the possibilities of diminishing the catalyst levels in metallic coper‐mediated RDRP (Cu(0)‐RDRP) and atom transfer radical polymerization (ATRP) of a widely used functional monomer, glycidyl methacrylate (GMA), targeting a low MW of approximately 3000. Both Cu wire‐ and powder‐catalyzed Cu(0)‐RDRP provided well‐defined, low‐MW poly(GMA) at quantitative conversions when using an inexpensive PMDETA ligand in DMSO. However, only with Cu powder, the contamination of the final polymerization mixture with Cu species could be efficiently diminished to ≤66 ppm while maintaining the polymerization control. Additionally, the in situ block copolymerization was successfully demonstrated, furnishing a poly(GMA)‐b‐poly(MMA) mixture containing only 39 ppm of Cu in a process facilitated by the intrinsic reductive properties of the GMA's epoxide groups. Significantly, the targeted low‐MW poly(GMA) could also be synthesized by low‐catalyst‐concentration ATRP (CuBr/PMDETA system), obtaining well‐defined polymers with quantitative conversions at ca 50 ppm of Cu in the final mixture, both at r.t. and 50 °C.
Since their addition to the polymer-architecture portfolio, gradient copolymers have attracted significant attention. Up to now, however, the existence of the intramolecular composition gradient must ...have been ascertained by sampling during living copolymerization because a reliable method for the detection of the composition gradient in the finalized copolymer had not been established yet. Here we show that MALDI-ToF mass spectrometry not only identifies imperfect, i.e. prematurely terminated copolymers but these copolymers can be used as “time capsules” which provide information on composition evolution and the intramolecular composition gradient.
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•MALDI-ToF MS detects the imperfect copolymers in the samples prepared by CRP.•imperfect copolymers carry the information on the composition evolution.•compositional distribution is not indicative of the copolymer sequence arrangement.
