@article{KayaDebsharmaSchlaadetal.2020, author = {Kaya, Kerem and Debsharma, Tapas and Schlaad, Helmut and Yagci, Yusuf}, title = {Cellulose-based polyacetals by direct and sensitized photocationic ring-opening polymerization of levoglucosenyl methyl ether}, series = {Polymer Chemistry}, volume = {11}, journal = {Polymer Chemistry}, number = {43}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1759-9954}, doi = {10.1039/d0py01307b}, pages = {6884 -- 6889}, year = {2020}, abstract = {This study aims to explore the photoinitiated cationic ring-opening polymerization of levoglucosenyl methyl ether (LGME), a chemical obtained from the most abundant biomass - cellulose. Direct and sensitized photopolymerizations of LGME using photoinitiators acting at the near UV or visible range in conjunction with diphenyliodonium hexafluoroantimonate (DPI) yielded unsaturated polyacetals with varying molar masses and distributions.}, language = {en} } @article{DebsharmaSchmidtLaschewskyetal.2021, author = {Debsharma, Tapas and Schmidt, Bernd and Laschewsky, Andre and Schlaad, Helmut}, title = {Ring-opening metathesis polymerization of unsaturated carbohydrate derivatives}, series = {Macromolecules : a publication of the American Chemical Society}, volume = {54}, journal = {Macromolecules : a publication of the American Chemical Society}, number = {6}, publisher = {American Chemical Society}, address = {Washington}, issn = {0024-9297}, doi = {10.1021/acs.macromol.0c02821}, pages = {2720 -- 2728}, year = {2021}, abstract = {A series of biomass-derived levoglucosenyl alkyl ethers (alkyl = methyl, ethyl, n-propyl, isopropyl, and n-butyl) were synthesized and polymerized by ring-opening olefin metathesis polymerization using the Grubbs catalyst C793 at room temperature. Polymerizations were successfully performed in conventional solvents such as 1,4-dioxane and dichloromethane as well as in polar aprotic "green" solvents such as 2-methyltetrahydrofuran, dihydrolevoglucosenone (Cyrene), and ethyl acetate. The prepared polyacetals with degrees of polymerization of similar to 100 exhibit Schulz-Flory-type molar mass distributions and are thermoplastic materials with rather low glass transition temperatures in the range of 43-0 degrees C depending on the length of the alkyl substituent. Kinetic studies revealed that the polymerization proceeded rapidly to a steady state with a certain minimum monomer concentration threshold. When the steady state was reached, just about half of the [Ru] catalyst had been effective to initiate the polymerization, indicating that the initiation step was a slow process. The remaining catalyst was still active and did no longer react with monomers but with in-chain double bonds, cutting the formed polymer chains into shorter fragments. In the long term, all catalyst was consumed and propagating [Ru] chain ends were deactivated by the elimination of [Ru] from the chain ends to form inactive chains with terminal aldehyde groups.}, language = {en} } @article{KeckeisZellerJungetal.2021, author = {Keckeis, Philipp and Zeller, Enriko and Jung, Carina and Besirske, Patricia and Kirner, Felizitas and Ruiz-Agudo, Cristina and Schlaad, Helmut and C{\"o}lfen, Helmut}, title = {Modular toolkit of multifunctional block copoly(2-oxazoline)s for the synthesis of nanoparticles}, series = {Chemistry - a European journal}, volume = {27}, journal = {Chemistry - a European journal}, number = {32}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.202101327}, pages = {8283 -- 8287}, year = {2021}, abstract = {Post-polymerization modification provides an elegant way to introduce chemical functionalities onto macromolecules to produce tailor-made materials with superior properties. This concept was adapted to well-defined block copolymers of the poly(2-oxazoline) family and demonstrated the large potential of these macromolecules as universal toolkit for numerous applications. Triblock copolymers with separated water-soluble, alkyne- and alkene-containing segments were synthesized and orthogonally modified with various low-molecular weight functional molecules by copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) and thiol-ene (TE) click reactions, respectively. Representative toolkit polymers were used for the synthesis of gold, iron oxide and silica nanoparticles.}, language = {en} } @article{DasNoackSchlaadetal.2020, author = {Das, Abhijna and Noack, Sebastian and Schlaad, Helmut and Reiter, G{\"u}nter and Reiter, Renate}, title = {Exploring pathways to equilibrate Langmuir polymer films}, series = {Langmuir}, volume = {36}, journal = {Langmuir}, number = {28}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/acs.langmuir.0c01268}, pages = {8184 -- 8192}, year = {2020}, abstract = {Focusing on the phase-coexistence region in Langmuir films of poly(L-lactide), we investigated changes in nonequilibrated morphologies and the corresponding features of the isotherms induced by different experimental pathways of lateral compression and expansion. In this coexistence region, the surface pressure II was larger than the expected equilibrium value and was found to increase upon compression, i.e., exhibited a nonhorizontal plateau. As shown earlier by using microscopic techniques [Langmuir 2019, 35, 6129-6136], in this plateau region, well-ordered mesoscopic clusters coexisted with a surrounding matrix phase. We succeeded in reducing Pi either by slowing down the rate of compression or through increasing the waiting time after stopping the movement of the barriers, which allowed for relaxations in the coexistence region. Intriguingly, the most significant pressure reduction was observed when recompressing a film that had already been compressed and expanded, if the recompression was started from an area value smaller than the one anticipated for the onset of the coexistence region. This observation suggests a "self-seeding" behavior, i.e., pre-existing nuclei allowed to circumvent the nucleation step. The decrease in Pi was accompanied by a transformation of the initially formed metastable mesoscopic clusters into a thermodynamically favored filamentary morphology. Our results demonstrate that it is practically impossible to obtain fully equilibrated coexisting phases in a Langmuir polymer film, neither under conditions of extremely slow continuous compression nor for long waiting times at a constant area in the coexistence region which allow for reorganization.}, language = {en} } @article{HessSchmidtSchlaad2020, author = {Hess, Andreas and Schmidt, Bernhard Volkmar Konrad Jakob and Schlaad, Helmut}, title = {Aminolysis induced functionalization of (RAFT) polymer-dithioester with thiols and disulfides}, series = {Polymer Chemistry}, volume = {11}, journal = {Polymer Chemistry}, number = {48}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1759-9954}, doi = {10.1039/d0py01365j}, pages = {7677 -- 7684}, year = {2020}, abstract = {A series of polystyrene- and poly(methyl methacrylate)-dithioesters was subjected to aminolysis under ambient atmospheric conditions, i.e., in the presence of oxygen. Polymer disulfide coupling by oxidation occurred within tens of minutes and the yield of disulfide-coupled polymer increased with decreasing polymer molar mass. Oxidation of thiolates is usually an unwanted side reaction, here it is employed to obtain exclusively polymeric mixed disulfides through in situ aminolysis/functionalization in the presence of a thiol. The in situ aminolysis/functionalization in the presence of a disulfide, Ellman's reagent or polymer disulfide, resulted in the exclusive formation of polymer-dithionitrobenzoic acid, which can be further reacted with a thiol to exchange the terminal functionality, or block copolymer with dynamic disulfide linker, respectively.}, language = {en} } @article{MaticHessSchanzenbachetal.2020, author = {Matic, Aleksandar and Hess, Andreas and Schanzenbach, Dirk and Schlaad, Helmut}, title = {Epoxidized 1,4-polymyrcene}, series = {Polymer chemistry}, volume = {11}, journal = {Polymer chemistry}, number = {7}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1759-9954}, doi = {10.1039/c9py01783f}, pages = {1364 -- 1368}, year = {2020}, abstract = {1,4-Polymyrcene was synthesized by anionic polymerization and epoxidized using meta-chloroperbenzoic acid. Samples with different degrees of epoxidation (25\%, 49\%, 74\%, and 98\%) were prepared and examined according to their chemical and thermal properties. Epoxidation was found to increase the glass transition temperature (T-g = 14 degrees C for the 98\% epoxidized 1,4-polymyrcene) as well as the shelf live (>10 months). The trisubstituted epoxide groups were remarkably stable against nucleophiles under basic conditions but cross-linked or hydrolyzed in the presence of an acid. Also, highly epoxidized 1,4-polymyrcene readily cross-linked upon annealing at 260 degrees C to produce an epoxy resin.}, language = {en} } @article{AlNajiSchlaadAntonietti2020, author = {Al-Naji, Majd and Schlaad, Helmut and Antonietti, Markus}, title = {New (and old) monomers from biorefineries to make polymer chemistry more sustainable}, series = {Macromolecular rapid communications}, volume = {42}, journal = {Macromolecular rapid communications}, number = {3}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1336}, doi = {10.1002/marc.202000485}, pages = {11}, year = {2020}, abstract = {This opinion article describes recent approaches to use the "biorefinery" concept to lower the carbon footprint of typical mass polymers, by replacing parts of the fossil monomers with similar or even the same monomer made from regrowing dendritic biomass. Herein, the new and green catalytic synthetic routes are for lactic acid (LA), isosorbide (IS), 2,5-furandicarboxylic acid (FDCA), and p-xylene (pXL). Furthermore, the synthesis of two unconventional lignocellulosic biomass derivable monomers, i.e., alpha-methylene-gamma-valerolactone (MeGVL) and levoglucosenol (LG), are presented. All those have the potential to enter in a cost-effective way, also the mass market and thereby recover lost areas for polymer materials. The differences of catalytic unit operations of the biorefinery are also discussed and the challenges that must be addressed along the synthesis path of each monomers.}, language = {en} } @article{LuedeckeSchlaad2021, author = {L{\"u}decke, Nils and Schlaad, Helmut}, title = {Inspired by mussel adhesive protein}, series = {Polymer Chemistry}, volume = {12}, journal = {Polymer Chemistry}, number = {37}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1759-9962}, doi = {10.1039/d1py00679g}, pages = {5310 -- 5319}, year = {2021}, abstract = {A set of new functionalized poly(2-oxazoline) homopolymers and copolymers carrying protected catecholic side chains were prepared by microwave-assisted cationic ring-opening (co)polymerization. The copolymerizations of 2-ethyl-2-oxazoline with either 2-(3,4-dimethoxyphenyl)-, 2-(3,4-dimethoxybenzyl)-, or 2-(3,4-dimethoxycinnamyl)-2-oxazoline (comonomer ratio 90 : 10) produced gradient or random copolymers with narrow molar mass distributions. During the copolymerization with the 2-(3,4-dimethoxycinnamyl)-2-oxazoline, however, chain coupling reactions occurred at monomer conversions of >50\%, supposedly via Michael-type addition of intermediately formed ketene N,O-acetal end groups to 3,4-dimethoxycinnamyl amide side chains. A poly[(2-ethyl-2-oxazoline)-grad-(2-(3,4-dimethoxyphenyl)-2-oxazoline)] was examplarily subjected to partial demethylation and acidic hydrolysis to give a hydrophilic copolymer carrying both catecholic and cationic units, which is designed as a bioinspired adhesive copolymer mimicking mussel adhesive protein.}, language = {en} } @article{GlatzelNoackSchanzenbachetal.2020, author = {Glatzel, Julia and Noack, Sebastian and Schanzenbach, Dirk and Schlaad, Helmut}, title = {Anionic polymerization of dienes in 'green' solvents}, series = {Polymer international}, volume = {70}, journal = {Polymer international}, number = {2}, publisher = {Wiley}, address = {Hoboken}, issn = {0959-8103}, doi = {10.1002/pi.6152}, pages = {181 -- 184}, year = {2020}, abstract = {Isoprene and beta-myrcene were polymerized by anionic polymerization in bulk and in the 'green' ether solvents cyclopentyl methyl ether and 2-methyltetrahydrofuran and, for comparison, in cyclohexane and tetrahydrofuran. The polydienes produced in bulk and in cyclohexane contained high amounts of 1,4 units (>90\%) whereas those produced in ether solvents were rich in 1,2 and 3,4 units (36\%-86\%). Comparison of the microstructures and glass transition temperatures of the polydienes obtained in the various solvents suggests that conventionally used solvents can be substituted by environmentally more friendly alternatives.}, language = {en} } @article{DevRoeslerSchlaad2021, author = {Dev, Akhil and R{\"o}sler, Alexander and Schlaad, Helmut}, title = {Limonene as a renewable unsaturated hydrocarbon solvent for living anionic polymerization of β-myrcene}, series = {Polymer chemistry}, volume = {12}, journal = {Polymer chemistry}, number = {21}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1759-9954}, doi = {10.1039/d1py00570g}, pages = {3084 -- 3087}, year = {2021}, abstract = {The acyclic monoterpene beta-myrcene is polymerized by anionic polymerization at room temperature using sec-butyllithium as the initiator and the cyclic monoterpene DL-limonene as an unsaturated hydrocarbon solvent. The polymerization is a living process and allows production of polymyrcenes with narrow molar mass distribution ((sic) similar to 1.06) and high content of 1,4 units (similar to 90\%) as well as block copolymers.}, language = {en} } @article{BehrendtSchlaad2017, author = {Behrendt, Felix Nicolas and Schlaad, Helmut}, title = {Metathesis polymerization of cystine-based macrocycles}, series = {Polymer Chemistry}, volume = {8}, journal = {Polymer Chemistry}, number = {2}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1759-9954}, doi = {10.1039/c6py01864e}, pages = {366 -- 369}, year = {2017}, abstract = {Macrocycles based on L-cystine were synthesized by ring-closing metathesis (RCM) and subsequently polymerized by entropy-driven ring-opening metathesis polymerization (ED-ROMP). Monomer conversion reached similar to 80\% in equilibrium and the produced poly (ester-amine-disulfide-alkene)s exhibited apparent molar masses (M-w(app)) of up to 80 kDa and dispersities (D) of similar to 2. The polymers can be further functionalized with acid anhydrides and degraded by reductive cleavage of the main-chain disulfide.}, language = {en} } @article{ChenSongZhaoetal.2018, author = {Chen, Ye and Song, Qilei and Zhao, Junpeng and Gong, Xiangjun and Schlaad, Helmut and Zhang, Guangzhao}, title = {Betulin-Constituted multiblock amphiphiles for broad-spectrum protein resistance}, series = {ACS applied materials \& interfaces}, volume = {10}, journal = {ACS applied materials \& interfaces}, number = {7}, publisher = {American Chemical Society}, address = {Washington}, issn = {1944-8244}, doi = {10.1021/acsami.7b16255}, pages = {6593 -- 6600}, year = {2018}, abstract = {Multiblock-like amphiphilic polyurethanes constituted by poly(ethylene oxide) and biosourced betulin are designed for antifouling and synthesized by a convenient organocatalytic route comprising tandem chain-growth and step-growth polymerizations. The doping density of betulin (D-B) in the polymer chain structure is readily varied by a mixed-initiator strategy. The spin-coated polymer films exhibit unique nanophase separation and protein resistance behaviors. Higher D-B leads to enhanced surface hydrophobicity and, unexpectedly, improved protein resistance. It is found that the surface holds molecular-level heterogeneity when D-B is substantially high due to restricted phase separation; therefore, broad-spectrum protein resistance is achieved despite considerable surface hydrophobicity. As D-B decreases, the distance between adjacent betulin units increases so that hydrophobic nanodomains are formed, which provide enough landing areas for relatively small-sized proteins to adsorb on the surface.}, language = {en} } @article{BehrendtSchlaad2018, author = {Behrendt, Felix Nicolas and Schlaad, Helmut}, title = {Entropy-Driven Ring-Opening Disulfide Metathesis Polymerization for the Synthesis of Functional Poly(disulfide)s}, series = {Macromolecular rapid communications}, volume = {39}, journal = {Macromolecular rapid communications}, number = {6}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1336}, doi = {10.1002/marc.201700735}, pages = {4}, year = {2018}, abstract = {Metal-free entropy-driven disulfide metathesis polymerization of unsaturated L-cystine based macrocycles produces high-molar-mass heterofunctional poly(disulfide)s, i.e., poly(ester-disulfide-alkene) and poly(amide-disulfide-alkene); M-w(app) = 44-60 kDa, (sic) > 1.7. The polymerization is fast and reaches equilibrium within 1-5 minutes (monomer conversion 70-90\%) in polar aprotic solvents such as N,N-dimethylacetamide, dimethylsulfoxide, or y-valerolactone. Thiol-terminated polymers are stable in bulk or when dissolved in weakly polar solvents, but rapidly depolymerize in dilute polar solution.}, language = {en} } @article{MaticSchlaad2018, author = {Matic, Aleksandar and Schlaad, Helmut}, title = {Thiol-ene photofunctionalization of 1,4-polymyrcene}, series = {Polymer international}, volume = {67}, journal = {Polymer international}, number = {5}, publisher = {Wiley}, address = {Hoboken}, issn = {0959-8103}, doi = {10.1002/pi.5534}, pages = {500 -- 505}, year = {2018}, abstract = {1,4-Polymyrcene was synthesized by anionic polymerization of -myrcene and was subjected to photochemical functionalization with various thiols (i.e. methyl thioglycolate, methyl 3-mercaptopropionate, butyl 3-mercaptopropionate, ethyl 2-mercaptopropionate and 2-methyl-2-propanethiol) using benzophenone/UV light as the radical source. The yield of thiol addition to the trisubstituted double bonds of 1,4-polymyrcene decreased in the order 1 degrees thiol (ca 95\%) > 2 degrees thiol (ca 80\%) > 3 degrees thiol (<5\%), due to the reversibility of the thiol-ene reaction. Remarkably, thiol addition to the side-chain double bonds was 8 - 10 times (1 degrees thiol) or 24 times (2 degrees thiol) faster than to the main-chain double bonds, which can be explained by the different accessibility of the double bonds and steric hindrance. Despite the use of a 10-fold excess of thiol with respect to myrcene units, the thiol-ene addition was accompanied by chain coupling reactions, which in the extreme case of 3 degrees thiol (or in the absence of thiol) resulted in the formation of insoluble crosslinked material. As an example, a methyl-thioglycolate-functionalized 1,4-polymyrcene was saponified/crosslinked to give submicron polyelectrolyte particles in dilute alkaline solution. (c) 2018 Society of Chemical Industry}, language = {en} } @article{VacogneWeiTaueretal.2018, author = {Vacogne, Charlotte Dominique and Wei, Chunxiang and Tauer, Klaus and Schlaad, Helmut}, title = {Self-assembly of alpha-helical polypeptides into microscopic and enantiomorphic spirals}, series = {Journal of the american chemical society}, volume = {140}, journal = {Journal of the american chemical society}, number = {36}, publisher = {American Chemical Society}, address = {Washington}, issn = {0002-7863}, doi = {10.1021/jacs.8b06503}, pages = {11387 -- 11394}, year = {2018}, abstract = {Helical structures are ubiquitous in biological materials and often serve a structural purpose. Bioinspired helical materials can be challenging to synthesize and rarely reach the degree of hierarchy of their natural counterparts. Here we report the first example of particles synthesized by direct emulsification of polypeptides found to display spiral morphologies in the dry state. The polypeptides were alpha-helical homo- and copolypeptides of gamma-benzyl glutamate and allylglycine. The chirality of the spirals was controlled by the chirality of the alpha-helices. Notably, right-handed alpha-helical polypeptides (rich in 1, residues) produced clockwise spirals, whereas left-handed alpha-helical polypeptides (rich in D residues) produced the enantiomorphs, i.e., counterclockwise spirals. The disruption of the alpha-helical conformation by the introduction of chiral defects led to less regular spirals and in some cases their suppression. A hypothesis for the transmission of helicity and chirality from a molecular to a higher hierarchical level, involving fibril bundling of coiled alpha-helices, is proposed.}, language = {en} } @article{GoldhahnSchubertSchlaadetal.2018, author = {Goldhahn, Christian and Schubert, Jonas and Schlaad, Helmut and Ferri, James K. and Fery, Andreas and Chanana, Munish}, title = {Synthesis of Metal@Protein@Polymer Nanoparticles with Distinct Interfacial and Phase Transfer Behavior}, series = {Chemistry of materials : a publication of the American Chemical Society}, volume = {30}, journal = {Chemistry of materials : a publication of the American Chemical Society}, number = {19}, publisher = {American Chemical Society}, address = {Washington}, issn = {0897-4756}, doi = {10.1021/acs.chemmater.8b02314}, pages = {6717 -- 6727}, year = {2018}, abstract = {In this study, we present a novel and facile method for the synthesis of multiresponsive plasmonic nanoparticles with an interesting interfacial behavior. We used thiol-initiated photopolymerization technique to graft poly(N-isopropylacrylamide) onto the surface of protein-coated gold nanoparticles. The combination of the protein bovine serum albumin with the thermoresponsive polymer leads to smart hybrid nanoparticles, which show a stimuli-responsive behavior of their aggregation and a precisely controllable phase transfer behavior. Three interconnected stimuli, namely, temperature, ionic strength, and pH, were identified as property tuning switches. The aggregation was completely reversible and was quantified by determining Smoluchowski's instability ratios with time-resolved dynamic light scattering. The tunable hydrophobicity via the three stimuli was used to study interfacial activity and phase transfer behavior of the nanoparticles at an octanol/water interface. Depending on the type of coating (i.e., protein or protein/polymer) as well as the three external stimuli, the nanoparticles either remained in the aqueous phase (aggregated or nonaggregated), accumulated at the oil/water interface, wet the glass wall between the glass vial and the octanol phase, or even crossed the oil/water interface. Such smart and interfacially active nanoparticles with external triggers that are capable of crossing oil/water interfaces under physiological conditions open up new avenues for a variety of applications ranging from the development of drug-delivery nanosystems across biological barriers to the preparation of new catalytic materials.}, language = {en} } @article{HardyBertinTorresRendonetal.2018, author = {Hardy, John G. and Bertin, Annabelle and Torres-Rendon, Jose Guillermo and Leal-Egana, Aldo and Humenik, Martin and Bauer, Felix and Walther, Andreas and C{\"o}lfen, Helmut and Schlaad, Helmut and Scheibel, Thomas R.}, title = {Facile photochemical modification of silk protein-based biomaterials}, series = {Macromolecular bioscience}, volume = {18}, journal = {Macromolecular bioscience}, number = {11}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1616-5187}, doi = {10.1002/mabi.201800216}, pages = {6}, year = {2018}, abstract = {Silk protein-based materials show promise for application as biomaterials for tissue engineering. The simple and rapid photochemical modification of silk protein-based materials composed of either Bombyx mori silkworm silk or engineered spider silk proteins (eADF4(C16)) is reported. Radicals formed on the silk-based materials initiate the polymerization of monomers (acrylic acid, methacrylic acid, or allylamine) which functionalize the surface of the silk materials with poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), or poly(allylamine) (PAAm). To demonstrate potential applications of this type of modification, the polymer-modified silks are mineralized. The PAA- and PMAA-functionalized silks are mineralized with calcium carbonate, whereas the PAAm-functionalized silks are mineralized with silica, both of which provide a coating on the materials that may be useful for bone tissue engineering, which will be the subject of future investigations.}, language = {en} } @article{ZhengBaiTaoetal.2018, author = {Zheng, Botuo and Bai, Tianwen and Tao, Xinfeng and Schlaad, Helmut and Ling, Jun}, title = {Identifying the Hydrolysis of Carbonyl Sulfide as a Side Reaction Impeding the Polymerization of N-Substituted Glycine N-Thiocarboxyanhydride}, series = {Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences}, volume = {19}, journal = {Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences}, number = {11}, publisher = {American Chemical Society}, address = {Washington}, issn = {1525-7797}, doi = {10.1021/acs.biomac.8b01119}, pages = {4263 -- 4269}, year = {2018}, abstract = {Polypeptoids are noticeable biological materials due to their versatile properties and various applications in drug delivery, surface modification, self-assembly, etc. N-Substituted glycine N-thiocarboxyanhydrides (NNTAs) are more stable monomers than the corresponding N-carboxyanhydrides (NNCAs) and enable one to prepare polypeptoids via ring-opening polymerization even in the presence of water. However, larger amounts of water (>10,000 ppm) cause inhibition of the polymerization. Herein, we discover that during polymerization hydrogen sulfide evolves from the hydrolysis of carbonyl sulfide, which is the byproduct of ring-opening reaction, and reacts with NNTA to produce cyclic oligopeptoids. The capture of N-ethylethanethioic acid as an intermediate product confirms the reaction mechanism together with density functional theory quantum computational results. By bubbling the polymerization solution with argon, the side reaction can be suppressed to allow the synthesis of polysarcosine with high molar mass (M-n = 11,200 g/mol, D = 1.25) even in the presence of similar to 10,000 ppm of water.}, language = {en} } @article{LuedeckeWeidnerSchlaad2019, author = {L{\"u}decke, Nils and Weidner, Steffen M. and Schlaad, Helmut}, title = {Poly(2-oxazoline)s Based on Phenolic Acids}, series = {Macromolecular rapid communications}, volume = {41}, journal = {Macromolecular rapid communications}, number = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1336}, doi = {10.1002/marc.201900404}, pages = {5}, year = {2019}, abstract = {A series of phenolic-acid-based 2-oxazoline monomers with methoxy-substituted phenyl and cinnamyl side chains is synthesized and polymerized in a microwave reactor at 140 °C using methyl tosylate as the initiator. The obtained poly(2-oxazoline)s are characterized by NMR spectroscopy, MALDI-TOF mass spectrometry, and size-exclusion chromatography (SEC). Kinetic studies reveal that the microwave-assisted polymerization is fast and completed within less than ≈10 min for low monomer-to-initiator ratios of ≤25. Polymers with number-average molar masses of up to 6500 g mol-1 and low dispersity (1.2-1.3) are produced. The aryl methyl ethers are successfully cleaved with aluminum triiodide/N,N′-diisopropylcarbodiimide to give a poly(2-oxazoline) with pendent catechol groups.}, language = {en} } @article{NoackSchanzenbachKoetzetal.2018, author = {Noack, Sebastian and Schanzenbach, Dirk and Koetz, Joachim and Schlaad, Helmut}, title = {Polylactide-based amphiphilic block copolymers}, series = {Macromolecular rapid communications}, volume = {40}, journal = {Macromolecular rapid communications}, number = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1022-1336}, doi = {10.1002/marc.201800639}, pages = {6}, year = {2018}, abstract = {The aqueous self-assembly behavior of a series of poly(ethylene glycol)-poly(l-/d-lactide) block copolymers and corresponding stereocomplexes is examined by differential scanning calorimetry, dynamic light scattering, and transmission electron microscopy. Block copolymers assemble into spherical micelles and worm-like aggregates at room temperature, whereby the fraction of the latter seemingly increases with decreasing lactide weight fraction or hydrophobicity. The formation of the worm-like aggregates arises from the crystallization of the polylactide by which the spherical micelles become colloidally unstable and fuse epitaxically with other micelles. The self-assembly behavior of the stereocomplex aggregates is found to be different from that of the block copolymers, resulting in rather irregular-shaped clusters of spherical micelles and pearl-necklace-like structures.}, language = {en} }