Polydl-lactide-b-[oligo(ethylene glycol) methyl ether (meth)acrylate)] block copolymers. Synthesis, characterization, micellization behavior in aqueous solutions and encapsulation of model hydrophobic compounds

A series of well-defined polydl -lactide-b-[oligo(ethylene glycol) methyl ether (meth)acrylate)] (PDLLA-b-POEG[M]A) functional amphiphilic diblock copolymers was synthesized by employing a multistep procedure involving: (a) ring-opening polymerization of dl -lactide using n-decanol and stannous octoate as the initiating system, (b) esterification reaction of the PDLLA hydroxyl end groups with 2-bromoisobutyryl bromide, (c) atom transfer radical polymerization of OEG(M)A with the newly created bromoisobutyryl initiating site, and (d) incorporation of biotin or folic acid at the POEGA chain ends using click chemistry. The products were characterized by NMR spectroscopy and SEC analysis. The aggregation behavior of the synthesized block copolymers was investigated by dynamic light scattering at 25°C in aqueous solutions. The hydrophobic model compounds Nile red and pyrene were efficiently incorporated into the copolymer aggregates in aqueous solutions. High partition coefficient values were determined by fluorescence spectroscopy. © 2020 Wiley Periodicals, Inc

Poly(DL-lactide)-b-poly(N,N-dimethylamino-2-ethyl methacrylate): Synthesis, characterization, micellization behavior in aqueous solutions, and encapsulation of the hydrophobic drug dipyridamole

We synthesized a series of well-defined poly(DL-lactide)-b-poly(N,N- dimethylamino-2-ethyl methacrylate) (PDLLAb-PDMAEMA) amphiphilic diblock copolymers by employing a three-step procedure: (a) ring-opening polymerization (ROP) of DL-lactide using n-decanol and stannous octoate, Sn(Oct)2, as the initiating system, (b) reaction of the PDLLA hydroxyl end groups with bromoisobutyryl bromide, and (c) atom transfer radical polymerization, ATRP, of DMAEMA with the newly created bromoisobutyryl initiating site. The aggregation behavior of the prepared block copolymers was investigated by dynamic light scattering and ζ potential measurements at 25 °C in aqueous solutions of different pH values. The hydrophobic drug dipyridamole was efficiently incorporated into the copolymer aggregates in aqueous solutions of pH 7.40. High partition coefficient values were determined by fluorescence spectroscopy. © 2010 American Chemical Society

On the polymerization of alkyl methacrylates with the achiral dimethylzirconocene precursor Cp2ZrMe2

Polymerization of methyl methacrylate (MMA) by the three component catalytic system Cp2ZrMe2/B(C6 F5)3/ZnEt2 (1), in toluene, under thoroughly purified conditions, was found to produce polymers of high molecular weights (MW > 60 × 103), low polydispersities (MW/Mn = 1.12-1.22) and almost quantitative yields. The polymerization process is characterized by a pronounced induction period followed by a rapid and constant rate of polymerization. The molecular weight of PMMA increases by increasing the conversion and is proportional to the ratio of [MMA]0/[Zr]0, while MW/Mn remains intact, meaning that the present polymerization proceeds in a well-controlled fashion. Evidence for effects of [ZnEt2] and temperature in the molecular characteristics of the final products are also presented in this study. Moreover, the catalytic system 1 was found to catalyze the polymerization of other alkyl methacrylates (alkyl = n-butyl, n-hexyl) to high molecular weight syndiotactic materials, with narrow molecular weight distribution, in very high conversion. Well-controlled copolymerization of MMA with n-hexyl methacrylate was successful by the effective catalytic action of 1, leading to multiblock polymeric structures. Copolymerization of MMA with stearyl methacrylate was also achieved, with the above-mentioned catalytic system. Evidence for the aggregation of the polymeric products in THF and toluene solutions was found by static and dynamic light scattering. The comparison of the polymerization results of this work with other studies clearly shows that in order to obtain improved molecular characteristics, thorough purification protocols should be applied

Complex macromolecular architectures utilizing metallocene catalysts

Graft copolymers having poly(methyl methacrylate), PMMA, backbone and polystyrene, PS, polyisoprene, PI, poly(ethylene oxide), PEO, poly(2-methyl-1,3-pentadiene), P2MP, and PS-b-PI branches were prepared using the macromonomer methodology and high-vacuum techniques. The methacrylic macromonomers, mMM, were synthesized by anionic polymerization, whereas their homopolymerization and copolymerization with MMA were performed by metallocene catalyst. Relatively high macromonomer conversions were obtained in all cases. The parameters affecting the polymerization characteristics were examined. Well-defined poly(butyl methacrylate)-b-poly(methyl methacrylate) block copolymers were prepared for the first time by sequential addition of monomers starting from n-butyl methacrylate. The samples were characterized by size exclusion chromatography, SEC, 1H and 13C NMR spectroscopy, low-angle laser light scattering, LALLS, and differential scanning calorimetry, DSC

Metallocene-catalyzed copolymerization of MMA with anionically synthesized methacryloyl macromonomers

Well-defined graft copolymers with poly(methyl methacrylate) backbone and poly(styrene) (PS), poly(isoprene) (PI), or poly(dimethylsiloxane) (PDMS) branches were synthesized by combining anionic and metallocene catalyzed polymerization. The synthetic strategy involves the preparation of methacryloyl macromonomers of PS, PI, and PDMS by anionic polymerization, followed by copolymerization with methyl methacrylate using the highly reactive catalytic system Cp2ZrMe2/B(C6F5)3/ZnEt2. The macromonomers and the fractionated graft copolymers were characterized by size exclusion chromatography, low-angle laser light scattering, and 1H NMR spectroscopy

Zirconocene-catalyzed copolymerization of methyl methacrylate with other methacrylate monomers

Statistical copolymers of methyl methacrylate (MMA) with n-butyl-, s-butyl, t-butyl-, n-hexyl-, decyl-, stearyl-, allyl-, trimethylsilyl- and trimethylsilyloxyethyl methacrylate were prepared by zirconocene-catalyzed copolymerization. The reactivity ratios of MMA copolymers with butyl-, hexyl-, and stearyl methacrylate were estimated using the Finemann-Ross, the inverted Finemann-Ross, and the Kelen-Tüdos graphical methods. Structural parameters of the copolymers were obtained from the calculated dyad sequences, derived by using the reactivity ratios. The effect of the nature of the methacrylate ester group and the catalytic system used on the copolymer structure is discussed. The glass-transition temperature (Tg) values of MMA copolymers with butyl- and hexyl methacrylate were measured and examined in the frame of several theoretical equations, allowing the prediction of these Tg values. The best fit was obtained using Barton and Johnston equations, taking the monomer sequence distribution of the copolymers into account. © 2004 Wiley Periodicals, Inc

Ring-opening polymerization of lactones using zirconocene catalytic systems: Block copolymerization with methyl methacrylate

The ring-opening polymerization of ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL) using nine catalytic systems consisting of a combination of three C2V zirconocene complexes and three borate cocatalysts is discussed. The polymerizations proceed in a well-controlled manner, producing polymers with relatively high molecular weights and narrow molecular weight distributions. Kinetic experiments of the polymerization of ε-CL with the catalytic system Cp2ZrMe2/B(C 6F5)3 (1) showed a linear dependence between polymerization yield and molecular weight with time, as well as between the molecular weight with the molar ratio of the monomer over the catalyst [e-CL]/[Zr], indicating sufficient control of the polymerization reaction. The catalytic system (1) was utilized for the synthesis of well-defined block copolymers of MMA with ε-CL and δ-VL. All samples were characterized by size exclusion chroma-tography, nuclear magnetic resonance, and differential scanning calorimetry. © 2007 Wiley Periodicals, Inc

PH-responsive aggregates from double hydrophilic block copolymers carrying zwitterionic groups. Encapsulation of antiparasitic compounds for the treatment of leishmaniasis

A series of well-defined poly [(ethylene oxide)-b-2-(dimethylamino)ethyl methacrylate] (PEO-b-PDMAEMA) diblock copolymers were synthesized by atom transfer radical polymerization (ATRP) techniques. Post-polymerization reactions were performed to transform a portion of the tertiary amine groups of the PDMAEMA into phosphorozwitterions. The aggregation behavior of the prepared zwitterionic block copolymers was investigated by static and dynamic light scattering techniques at 25 and 37 °C, in weakly basic and acidic aqueous solutions. Antiparasitic drugs used for the treatment of Leishmania were incorporated into the copolymer aggregates. The effect of the solution pH, the zwitterion content, temperature, and the quantity of the incorporated drug on the aggregation behavior of the copolymers was tested. © 2007 American Chemical Society