To enhance the limited degradability of poly(ethylene glycol) (PEG), a straightforward method of synthesizing poly[(ethylene glycol)‐co‐(glycolic acid)] (P(EG‐co‐GA)) via a ruthenium‐catalyzed, post‐polymerization oxyfunctionalization of various PEGs is developed. Using this method, a set of copolymers with GA compositions of up to 8 mol% are prepared with minimal reduction in molecular weight (<10%) when compared to their commercially available starting materials. The P(EG‐co‐GA) copolymers are shown to undergo hydrolysis under mild conditions.
The synthesis of symmetric cyclo poly(ε‐caprolactone)–block–poly(l (d )‐lactide) (c(PCL–b–PL(D)LA)) by combining ring‐opening polymerization of ε‐caprolactone and lactides and subsequent click chemistry reaction of the linear precursors containing antagonist functionalities is presented. The two blocks can sequentially crystallize and self‐assemble into double crystalline spherulitic superstructures. The cyclic chain topology significantly affects both the nucleation and the crystallization of each constituent, as gathered from a comparison of the behavior of linear precursors and cyclic block copolymers. The stereochemistry of the PLA block does not have a significant effect on the nonisothermal crystallization of both linear and cyclo PCL‐b‐PDLA and PCL‐b‐PLLA copolymers.
A commercially available palladium N‐heterocyclic carbene (Pd‐NHC) precatalyst is used to initiate chain‐growth polymerization of 2‐bromo‐3‐hexyl‐5‐trimethylstannylthiophene. The molecular weight of the resultant poly(3‐hexylthiophene) can be modulated (7 to 73 kDa, Đ = 1.14 to 1.53) by varying the catalyst concentration. Mass spectrometry data confirm control over the polymer end groups and 1H NMR spectroscopy reveals that the palladium catalyst is capable of “ring‐walking”. A linear relationship between Mn and monomer conversion is observed. Atomic force microscopy and X‐ray scattering verify the regioregular nature of the resultant polythiophene.
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.
Well‐defined poly(2,5‐dihexyloxyphenylene‐1,4‐diyl) (PPP) is successfully synthesized by the Negishi catalyst‐transfer polycondensation (NCTP) using dilithium tetra(tert‐butyl)zincate (tBu4ZnLi2). The obtained PPP possesses the number‐averaged molecular weight (M n) values in the range of 2100–22 000 and the molar‐mass dispersity (Ð M) values in the range of 1.09–1.23. In addition, block copolymers containing PPP and poly(3‐hexylthiophene) (P3HT) segments (PPP‐b‐P3HT) are synthesized to confirm the feasibility of chain extension between the different monomers based on NCTP.
Temperature‐triggered switchable nanofibrous membranes are successfully fabricated from a mixture of cellulose acetate (CA) and poly(N‐isopropylacrylamide) (PNIPAM) by employing a single‐step direct electrospinning process. These hybrid CA‐PNIPAM membranes demonstrate the ability to switch between two wetting states viz. superhydrophilic to highly hydrophobic states upon increasing the temperature. At room temperature (23 °C) CA‐PNIPAM nanofibrous membranes exhibit superhydrophilicity, while at elevated temperature (40 °C) the membranes demonstrate hydrophobicity with a static water contact angle greater than 130°. Furthermore, the results here demonstrate that the degree of hydrophobicity of the membranes can be controlled by adjusting the ratio of PNIPAM in the CA‐PNIPAM mixture.
Poly(N‐isopropylacrylamide‐co‐3‐(trimethoxysilyl)propyl methacrylate), P(NIPAAm‐co‐TMSPMA), copolymers with relatively high TMSPMA contents without insoluble fraction are successfully synthesized. Subsequent sol–gel reactions in both the absence and presence of tetraethyl orthosilicate lead to gels with high gel fractions. The resulting gels undergo gel collapse at 28.6–28.7 °C, i.e., below that of poly(N‐isopropylacrylamide) homopolymer of 34.3 °C. Unexpectedly, the theophylline‐loaded hybrid gels release the drug not only below but also above the gel collapse temperature (GCT) with considerable rates and released amounts of drug. Surprisingly, evaluation of the sustained release profiles by the Korsmeyer–Peppas equation indicates that the release occurs by Fickian diffusion above GCT, which can be attributed to the lack of significant drug–polymer interaction at such temperatures. These results can be widely applied for the design and utilization of TMSPMA‐based sol–gel polymer hybrids with desired release profiles of solutes below and above GCT for a variety of applications.
The step‐wise solution self‐assembly of double crystalline organometallic poly(ferrocenyldimethylsilane)‐block‐poly(2‐iso‐propyl‐2‐oxazoline) (PFDMS‐b‐PiPrOx) diblock copolymers is demonstrated. Two block copolymers are obtained by copper‐catalyzed azide‐alkyne cycloaddition (CuAAC), featuring PFDMS/PiPrOx weight fractions of 46/54 (PFDMS30‐b‐PiPrOx75) and 30/70 (PFDMS30‐b‐PiPrOx155). Nonsolvent induced crystallization of PFDMS in acetone leads in both cases to cylindrical micelles with a PFDMS core. Afterward, the structures are transferred into water for sequential temperature‐induced crystallization of the PiPrOx corona, leading to hierarchical double crystalline superstructures, which are investigated using scanning electron microscopy, wide angle X‐ray scattering, and differential scanning calorimetry.
The formation of a poly(2,6‐carbazole) derivative during an electrochemical polymerization process is shown. Comparison of 3,5‐bis(9‐octyl‐9H‐carbazol‐2‐yl)pyridine and 3,5‐bis(9‐octyl‐9H‐carbazol‐3‐yl)pyridine by electrochemical and UV–Vis‐NIR spectroelectrochemical measurements and DFT (density functional theory) calculation prove the formation of a poly(2,6‐carbazole) derivative. Both of the compounds form stable and electroactive conjugated polymers.
Biocompatible lipo‐histidine hybrid materials conjugated with IR820 dye show pH‐sensitivity, efficient intracellular delivery of doxorubicin (Dox), and intrinsic targetability to cancer cells. These new materials form highly uniform Dox‐loaded nanosized vesicles via a self‐assembly process showing good stability under physiological conditions. The Dox‐loaded micelles are effective for suppressing MCF‐7 tumors, as demonstrated in vitro and in vivo. The combined mechanisms of the EPR effect, active internalization, endosomal‐triggered release, and drug escape from endosomes, and a long blood circulation time, clearly prove that the IR820 lipopeptide DDS is a safe theranostic agent for imaging‐guided cancer therapy.
A novel one‐component type II polymeric photoinitiator, poly(vinyl alcohol)–thioxanthone (PVA–TX), is synthesized by a simple acetalization process and characterized. PVA–TX enables photopolymerization of methyl methacrylate and acrylamide in both organic and aqueous media. Photopolymerization proceeds even in the absence of a co‐initiator since PVA–TX possesses both chromophoric and hydrogen donating sites in the structure.
An alkyne‐functionalized ruthenium(II) bis‐terpyridine complex is directly copolymerized with phenylacetylene by alkyne polymerization. The polymer is characterized by size‐exclusion chromatography (SEC), 1H NMR spectroscopy, cyclic voltammetry (CV) measurements, and thermal analysis. The photophysical properties of the polymer are studied by UV–vis absorption spectroscopy. In addition, spectro‐electrochemical measurements are carried out. Time‐resolved luminescence lifetime decay curves show an enhanced lifetime of the metal complex attached to the conjugated polymer backbone compared with the Ru(tpy)22+ model complex.
Herein, it is demonstrated that star pseudopolyrotaxanes (star‐pPRs) obtained from the inclusion complexation of α‐cyclodextrin (CD) and four‐branched star poly(ε‐caprolactone) (star‐PCL) organize into nanoplatelets in dimethyl sulfoxide at 35 °C. This peculiar property, not observed for linear pseudopolyrotaxanes, allows the processing of star‐pPRs while preserving their supramolecular assembly. Thus, original PCL:star‐pPR core:shell nanofibers are elaborated by coaxial electrospinning. The star‐pPR shell ensures the presence of available CD hydroxyl functions on the fiber surface allowing its postfunctionalization. As proof of concept, fluorescein isothiocyanate is grafted. Moreover, the morphology of the fibers is maintained due to the star‐pPR shell that acts as a shield, preventing the fiber dissolution during chemical modification. The proposed strategy is simple and avoids the synthesis of polyrotaxanes, i.e., pPR end‐capping to prevent the CD dethreading. As PCL is widely used for biomedical applications, this strategy paves the way for simple functionalization with any bioactive molecules.
The synthesis, characterization, and testing of a range of novel bio‐inspired L‐DOPA‐derived poly(ester amide)s is presented, using a widely applicable, straightforward chemistry. A model system is used to study and establish the monomer and polymer synthetic protocols, and to provide a set of optimum reaction conditions. It is further shown that fully biobased L‐DOPA‐containing adhesive tapes can be fabricated, which are positively evaluated in terms of their adhesive properties. The newly developed synthetic protocol constitutes a versatile platform for accessing and tailoring a plethora of relevant structures, including a variety of potentially biocompatible poly(ethylene glycol)‐based materials.
The preparation of multifunctional polymers and block copolymers by a straightforward one‐pot reaction process that combines enzymatic transacylation with light‐controlled polymerization is described. Functional methacrylate monomers are synthesized by enzymatic transacylation and used in situ for light‐controlled polymerization, leading to multifunctional methacrylate‐based polymers with well‐defined microstructure.
Furfuryl glycidyl ether (FGE) represents a highly versatile monomer for the preparation of reversibly cross‐linkable nanostructured materials via Diels–Alder reactions. Here, the use of FGE for the mid‐chain functionalization of a P2VP‐b‐PEO diblock copolymer is reported. The material features one furan moiety at the block junction, P2VP68‐FGE‐b‐PEO390, which can be subsequently addressed in Diels–Alder reactions using maleimide‐functionalized counterparts. The presence of the FGE moiety enables the introduction of dyes as model labels or the formation of hetero‐grafted brushes as shell on hybrid Au@Polymer nanoparticles. This renders P2VP68‐FGE‐b‐PEO390, a powerful tool for selective functionalization reactions, including the modification of surfaces.
A novel procedure has been developed for the Gilch reaction leading to poly(p‐phenylene vinylenes) (PPVs). In the first step, selective activation of the starting material is achieved at low temperature. Subsequently, controlled chain growth is induced by lighting the α‐halo‐p‐quinodimethane monomer. In contrast to the thermal Gilch polymerization, the photoinduced process allows adjusting crucial parameters such as intensity and energy of light. The progress of PPV formation can be followed visually or by in situ UV–vis spectroscopy. If the polymers are formed under appropriate conditions, they show very high molar masses, polydispersities in the common range, and higher constitutional homogeneity than thermally grown PPVs.
The fluorinated FI–Ti catalyst bis[N‐(3‐propylsalicylidene)‐pentafluoroanilinato] titanium(IV) dichloride (PFI) combined with dried methylaluminoxane (dMAO) is investigated for ethylene/1‐hexene copolymerization at 50 °C under atmospheric pressure. The reaction shows good livingness and has a high activity at high [H]/[E] molar ratios up to 14. Ultrahigh molecular weight (>1.4 × 106 g mol−1) copolymers with high 1‐hexene content (>25 mol%) are prepared. Kinetic parameters of the copolymerization with PFI are determined. The first‐order Markov statistics applies and the product of the reactivity ratios r1r2 is close to 1, giving random unit distributions.
Thermal field‐flow fractionation (ThFFF) is an interesting alternative to column‐based fractionation being able to address different molecular parameters including size and composition. Until today it has not been shown to be able to fractionate polymers of similar molar masses and chemical compositions by molecular topology. The present study demonstrates that poly(butyl methacrylates) with identical molar masses can be fractionated by ThFFF according to the topology of the butyl group. The influence of the solvent polarity on the thermal diffusion behavior of these polymers is presented and it is shown to have a significant influence on the fractionation of poly(n‐butyl methacrylate) and poly(t‐butyl methacrylate). Fractionation improves with increasing solvent polarity and solvent polarity may have a greater influence on fractionation than solvent viscosity. It is found that the thermal diffusion coefficient, DT, as well as the hydrodynamic diameter, Dh, exhibit increasing trends with increasing solvent polarity. The solvent quality has a significant influence on the fractionation. It is found that cyclohexane, being a theta solvent for poly(t‐butyl methacrylate) but not for poly(n‐butyl methacrylate), significantly improves the fractionation of the samples by decreasing the diffusion rate of the former but not the latter.
A straightforward and expeditious monotopic approach for the preparation of 1,2,3‐triazolium‐based poly(ionic liquids) (TPILs) is reported. It is based on the solvent‐ and catalyst‐free polyaddition of an α‐azide‐ω‐alkyne monomer in the presence of methyl iodide or N‐methyl bis[(trifluoromethyl)sulfonyl]imide alkylating agents. Poly(1,2,3‐triazole)s generated in bulk or by thermal azide–alkyne cycloaddition (AAC) are quaternized in‐situ to afford TPILs composed of 1,3,4‐ and 1,3,5‐trisubstituted 1,2,3‐triazolium units. The physical and ion‐conducting properties of the prepared samples are compared with the TPILs composed solely of 1,3,4‐trisubstituted 1,2,3‐triazolium units obtained through a multistep approach involving copper(I)‐catalyzed AAC polyaddition, quaternization of the 1,2,3‐triazole groups, and anion metathesis. TPILs obtained through the monotopic approach display thermal stabilities and ionic conductivities comparable to their pure regioisomeric analogues.
