Tin Bis Research Articles

Tacticity-Induced Changes in the Micellization and Degradation Properties of Poly(lactic acid)-block-poly(ethylene glycol) Copolymers

Poly(lactic acid)-block-poly(ethylene glycol) copolymers (PLA-b-PEG) featuring varying tacticities (atactic, heterotactic, isotactic) in the PLA block were synthesized and investigated for their micellar stability, degradation, and thermal properties. Utilizing tin(II) bis(2-ethylhexanoate), aluminum salan, and aluminum salen catalysts, the copolymers were synthesized through the ring-opening polymerization of d-, l-, rac-, or a blend of l- and rac-lactide using monomethoxy-poly(ethylene glycol) as a macroinitiator. The critical micelle concentration, which reflects the micellar stability, was probed using a fluorescence spectroscopic method with pyrene as the probe. The copolymers were degraded in a methanolic solution of 1,5,7-triaza-bicyclo[4.4.0]dec-5-ene and the degradation was measured by (1)H NMR spectroscopic and gel permeation chromatographic analyses. Differential scanning calorimetry and thermogravimetric analysis provided information on the thermal properties of the copolymers. Atactic and heterotactic microstructures in the PLA block resulted in lower micellar stability, as well as faster degradation and shorter erosion time compared to polymers with high isotactic enchainment (Pm). By modification of the Pm, micellar stability, degradation, and erosion rates of the copolymers can be tuned to specific biomedical applications. Interestingly, while tin(II) bis(2-ethylhexanoate) and aluminum salan-catalyzed PLA-b-PEG copolymers exhibited similar micellization behavior, the aluminum salen-catalyzed PLA-b-PEG exhibited unique behavior at high micelle concentration in the presence of the pyrene probe. This unique behavior can be attributed to the disintegration of the micelles through the interactions of long isotactic stereoblock segments.

Synthesis and characterization of an amphiphilic methoxy poly(l-lactide)-block-poly(glycidylmethacrylate) copolymer as a drug nanocarrier

AbstractPresent research is a preliminary report on the amphiphilic diblock copolymer (mPLA-b-PGMA) comprising hydrophobic methoxy poly(L-lactide) (mPLA) and hydrophilic poly(glycidyl methacrylate) (PGMA) segments was used as a promising drug carrier. Diblock copolymer was synthesized via ring opening polymerization (ROP) and atom transfer radical polymerization (ATRP) methods. Methanol first initiated ROP of L-lactide in the presence of tin(II)bis(2-ethylhexanoate) (Sn(oct)2) as a catalyst. The resulting monohydroxyl-terminated polylactic acid (mPLA) was subsequently converted to a bromine-ended macroinitiator (mPLA-Br) by esterification with 2-bromisobutyryl bromide. The copolymer mPLA-b-PGMA was synthesized in a subsequent ATRP of GMA. The obtained polymers were characterized by means of 1H NMR, FTIR, DSC and TGA. The copolymer mPLA-b- PGMA self-assembled into nanoscale micelles in aqueous solutions, as investigated by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The TEM image of polymeric micelles showed that the micelles were spherical in shape and that their diameters were in the range of 80-140 nm. Then by using the naproxen as a hydrophobic model drug, the drug-loaded micelles with 81.18 % loading efficiency and 16.24 % loading capacity were prepared. Moreover, in vitro release study of naproxen was performed using dialysis bag in phosphate-buffered solution at 37°C and pH at 7.4. Accordingly, these polymeric micelles may provide as an effective drug carrier for controlled drug release.

Synthesis and characterizations of poly(ethylene-co-vinylalcohol)-grafted-poly(3-hydroxybutyrate-co-hydroxyvalerate) copolymers

Poly(ethylene-co-vinylalcohol)-grafted-poly(3-hydroxybutyrate-co-hydroxyvalerate) (EVOH-g-PHBV) was prepared by a catalyzed grafting of PHBV onto immiscible EVOH. These reactions were performed at high temperature in the molten state. The choices of Tin(II) bis(2-ethylhexanoate) (Sn(Oct)2) and 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD), as catalyst, were justified by a first study in an internal mixer. The catalyst quantity, reaction temperature and reaction time were optimized to apply them in the conditions of a reactive extrusion process with a co-rotating twin screw extruder. High reaction temperature, from 180 °C to 220 °C, associated to intensive mixing led to efficient grafting of PHBV onto EVOH, compatible with short residence times required.Rheological, thermal and morphological analyses were conducted to characterize the obtained copolymers. Molecular weights were determined by SEC. SEM imaging were made on cryo-fractured surfaces of blends extruded with and without catalyst. In most of reaction conditions, a compatible blend was obtained with a fine micro phase separation. Grafted copolymers were only obtained when well defined and controlled conditions are applied.

A Facile Solution-Phase Approach to Transparent and Conducting ITO Nanocrystal Assemblies

Monodisperse 11 nm indium tin oxide (ITO) nanocrystals (NCs) were synthesized by thermal decomposition of indium acetylacetonate, In(acac)(3), and tin bis(acetylacetonate)dichloride, Sn(acac)(2)Cl(2), at 270 °C in 1-octadecene with oleylamine and oleic acid as surfactants. Dispersed in hexane, these ITO NCs were spin-cast on centimeter-wide glass substrates, forming uniform ITO NC assemblies with root-mean-square roughness of 2.9 nm. The assembly thickness was controlled by ITO NC concentrations in hexane and rotation speeds of the spin coater. Via controlled thermal annealing at 300 °C for 6 h under Ar and 5% H(2), the ITO NC assemblies became conductive and transparent with the 146 nm-thick assembly showing 5.2 × 10(-3) Ω·cm (R(s) = 356 Ω/sq) resistivity and 93% transparency in the visible spectral range--the best values ever reported for ITO NC assemblies prepared from solution phase processes. The stable hexane dispersion of ITO NCs was also readily spin-cast on polyimide (T(g) ~360 °C), and the resultant ITO assembly exhibited a comparable conductivity and transparency to the assembly on a glass substrate. The reported synthesis and assembly provide a promising solution to the fabrication of transparent and conducting ITO NCs on flexible substrates for optoelectronic applications.

ChemInform Abstract: Low‐Cost Copper Zinc Tin Sulfide Counter Electrodes for High‐Efficiency Dye‐Sensitized Solar Cells.

AbstractCu1.51Zn1.00Sn1.45S3.61 nanoparticles are prepared by injecting a solution of sulfur in oleylamine into a mixture of copper(II) acetylacetonate, zinc acetylacetonate, tin(IV) bis(acetylacetonate) dibromide, and oleylamine (225 °C, 1 h).

Synthesis and Characterization of Lactone Functional Macromonomers by End Group Deactivation and Their Use in Miktoarm Star Polymer

Newly designed miktoarm star-shaped copolymers made of poly[(benzyl methacrylate(BMA)-co-(ε-caprolacton)(CL)] and poly[(BMA-b-MMA-b-BMA)-co-ε-caprolacton)(CL)] were synthesized by combining ring-opening polymerization (ROP) of ε-caprolactone (CL) and poly(BMA) five membered lacton fuctionalized prepared via atom transfer radical polymerization (ATRP) of BMA, and ε-CL and P(BMA-b-MMA-b-BMA) dual functionalized diblock copolymer, in the presence of tin(II) bis(2-ethylhexanoate) (Sn(Oct)2). Although lactone ended poly(benzyl methacrylate) with ε-caprolactone monomer gave ring open polymerization by Sn(Oct)2, the macromonomer itself did not give any poly- merization The macromonomers, and the miktoarm star-shaped copolymers were analyzed by FT-IR and 1H-NMR spectroscopies and GPC (gel permeation chromatograph), Differential scanning calorimetry (DSC-50) and termo- gravimetric analysis (TGA-50). These copolymers exhibited the expected structure. The crystallization of star-shaped copolymers was studied by DSC. The results show that when the content of the BMA block increased, the Tm of the star-shaped block copolymer increased.

Organometallic and enzymatic catalysis for ring opening copolymerization of ε‐caprolactone and 4‐methyl‐ε‐caprolactone

AbstractA series of copolymers containing ε‐caprolactone (CL) and 4‐methyl‐ε‐caprolactone (MeCL) were synthesized by ring‐opening polymerization (ROP) using Tin(II) bis(2‐ethylhexanoate)(Sn(Oct)2) or Novozym 435 as catalyst. The molecular structure and weight of copolymers were determined by nuclear magnetic resonance (NMR) and size exclusion chromatography (SEC), respectively. Our kinetic study showed that the monomer reactivity ratios for CL (r1) and MeCL (r2) using Sn(Oct)2 as catalyst were estimated to be near unity and r1 × r2 = 1, indicating the random distribution of the monomers in the final copolymer. The results of DSC and XRD consistently indicated that the copolymers were inclined to be amorphous with the increasing of MeCL fraction. Microspheres were prepared from copolymers and characterized by SEM. The preliminary degradability and biocompatibility studies on these copolymers were also assessed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Tin oxide nanocrystals: controllable synthesis, characterization, optical properties and mechanistic insights into the formation process

A novel, surfactant-free, solution-phase method has been successfully developed for the synthesis of SnO2 nanocrystals using a solvothermal route. The nanocrystals having average diameters in the range 4–8 nm, have been synthesized by a non-aqueous sol–gel reaction using tin(IV) bis(acetylacetonate)dichloride, [(Sn(acac)2Cl2)] with benzyl alcohol as the reaction medium at 200 °C. The crystal structure, morphology, and sizes of the SnO2 nanocrystals have been determined by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman studies. Raman peaks at 627, 768 cm−1 characteristic of the rutile phase of bulk SnO2 are observed along with broad surface vibration modes in the range 400–600 cm−1. Optical properties of the nanocrystals have been explored by optical absorption and photoluminescence (PL). A blue shift of the optical band gap of the nanocrystals is observed due to size effects. The estimated band gap of the SnO2 nanocrystals from optical absorption data is found to be 3.81 eV. The photoluminescence spectrum showed broad UV as well as visible emission. Based on the GC-MS and carbon-13 NMR analysis of the final reaction solution, a formation mechanism encompassing the ether elimination and solvolysis of acetylacetonate ligand is proposed.

Atom transfer radical polymerization using activators regenerated by electron transfer of acrylonitrile in 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium hexafluorophospate

AbstractAtom transfer radical polymerization using activators regenerated by electron transfer (ARGET ATRP) of acrylonitrile (AN) was first approached with 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium tetrafluoroborate ([ecemim][BF4]) as reaction medium and tin(II) bis(2‐ethylhexanoate) (Sn(EH)2) as reducing agent in the presence of air. When compared with in bulk, an obvious increase of polymer isotacticity was observed for ARGET ATRP of AN in 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium hexafluorophospate ([ecemim][PF6]), the reaction rate of ARGET ATRP of AN in [ecemim][PF6] was higher and the polymerization process was better controlled. The block copolymer polyacrylonitrile‐block‐poly(methyl methacrylate) with molecular weight at 69,750, distribution at 1.34, and isotacticity at 0.36 was successfully obtained in [ecemim][PF6]. [Ecemim][PF6] and the catalyst system were recycled and reused and had no effect on the living nature of polymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Synthesis and characterization of a tin(ii) bis(phosphinoyl)methanediide complex: a stannavinylidene derivative

The reaction of [CH(2)(PPh(2)=NSiMe(3))(PPh(2)=S)] (1) with two equivalents of [Sn{N(SiMe(3))(2)}(2)] in refluxing toluene afforded novel tin(II) bis(phosphinoyl)methanediide complex 3. The structure of compound 3 has been determined by X-ray crystallography and DFT calculations. The topological analysis of the electron densities of compound 3 was performed.

Syntheses, Crystal Structure and Reactivity of Tin(II) Bis[N‐(diphenylphosphanyl)(2‐pyridylmethyl)amide

AbstractMetallation of N‐(diphenylphosphanyl)(2‐pyridylmethyl)amine with n‐butyllithium in toluene yields lithium N‐(diphenylphosphanyl)(2‐pyridylmethyl)amide (1), which crystallizes as a tetramer. Transamination of N‐(diphenylphosphanyl)(2‐pyridylmethyl)amine with an equimolar amount of Sn[N(SiMe3)2]2 leads to the formation of monomeric bis(trimethylsilyl)amido tin(II) N‐(diphenylphosphanyl)(2‐pyridylmethyl)amide (2). The addition of another equivalent of N‐(diphenylphosphanyl)(2‐pyridylmethyl)amine gives homoleptic tin(II) bis[N‐(diphenylphosphanyl)(2‐pyridylmethyl)amide] (3). In these complexes the N‐(diphenylphosphanyl)(2‐pyridylmethyl)amido groups act as bidentate bases through the nitrogen bases. At elevated temperatures HN(SiMe3)2 is liberated from bis(trimethylsilyl)amido tin(II) N‐(diphenylphosphanyl)(2‐pyridylmethyl)amide (2) yielding mononuclear tin(II) 1,2‐dipyridyl‐1,2‐bis(diphenylphosphanylamido)ethane (4) through a C–C coupling reaction. The three‐coordinate tin(II) atoms of 2 and 4 adopt trigonal pyramidal coordination spheres.

Synthesis of adaptative and amphiphilic polymer model conetworks by versatile combination of ATRP, ROP, and “Click chemistry”

Well-defined adaptative and amphiphilic polymer conetworks based on hydrophilic poly(N,N-dimethylamino-2-ethyl methacrylate) (PDMAEMA) and hydrophobic poly(e-caprolactone) (PCL) have been prepared by combination of ATRP, ROP, and Click chemistry. Telechelic α,ω-alkyne terminated PCL crosslinker was obtained by ring-opening polymerization (ROP) of CL in THF at 80 °C initiated by 1,4-butanediol and catalyzed by tin(II) bis 2-ethyl hexanoate (Sn(Oct) 2 ), followed by the quantitative esterification of hydroxyl end-groups by activated 4-pentynoic acid. In parallel, an azido-containing PDMAEMA-based copolymer was obtained in a three-step strategy involving primarily the copolymerization of DMAEMA with newly synthesized 2-(2-azidoethoxy)ethyl methacrylate (AEEMA) monomer. The latter was obtained by nucleophilic substitution of chloride atom from 2-(2-chloroethoxy)ethanol by an azide group followed by the esterification reaction of the hydroxyl group with methacrylic anhydride. The copolymerization was carried out in an equivolumic mixture of H 2 O and isopropanol at r.t. and initiated by a ω-bromoisobutyryl oligo PEO macroinitiator in the presence of various ligated copper(I)-based catalysts. In a last step, both polymer precursors were chemically linked by the Huisgen-1,3-dipolar cycloaddition in anhydrous THF at r.t. using CuBr complexed by 2,2'-bipyridine ligand as catalyst. Final material was characterized by the means of DSC and SEM, both attesting of a homogeneous distribution of the PCL crosslinkers and a highly porous structure in this new amphiphilic model conetworks.

Chlorinated polyethylene nanocomposites using PCL/clay nanohybrid masterbatches

Exfoliated nanocomposites were prepared by dispersion of poly(ε-caprolactone) (PCL) grafted montmorillonite nanohybrids used as masterbatches in chlorinated polyethylene (CPE). The PCL-grafted clay nanohybrids with high inorganic content were synthesized by in situ intercalative polymerization of ε-caprolactone between silicate layers organo-modified by alkylammonium cations bearing two hydroxyl functions. The polymerization was initiated by tin alcoholate species derived from the exchange reaction of tin(II) bis(2-ethylhexanoate) with the hydroxyl groups borne by the ammonium cations that organomodified the clay. These highly filled PCL nanocomposites (25 wt% in inorganics) were dispersed as masterbatches in commercial chlorinated polyethylene by melt blending. CPE-based nanocomposites containing 3–5 wt% of inorganics have been prepared. The formation of exfoliated nanocomposites was assessed both by wide-angle X-ray diffraction and transmission electron microscopy. The thermal and thermo-mechanical properties were studied as a function of the filler content, by differential scanning calorimetry and dynamic mechanical analysis, respectively. The mechanical properties were also assessed by tensile tests. The Young’s modulus of CPE is increased by a decade when a PCL-grafted clay masterbatch is exfoliated to reach 5 wt% of clay in the resulting nanocomposite. The influence of PCL-grafting on the properties of these nanocomposites was investigated by comparison with materials obtained with ungrafted-PCL.

Ring-Opening Polymerization of Lactide To Form a Biodegradable Polymer

In this laboratory activity for introductory organic chemistry, students carry out the tin(II) bis(2-ethylhexanoate)/benzyl alcohol mediated ring-opening polymerization of lactide to form the biodegradable polymer polylactide (PLA). As the mechanism of the polymerization is analogous to that of a transesterification reaction, the experiment can be used to demonstrate reactions of carboxylic acid derivatives. The polymerization can be successfully carried out using standard teaching laboratory (non-Schlenk) conditions. Analysis of polymer stereochemistry by 1H NMR and a discussion of the effect of monomer stereochemistry on the stereochemistry of the polymer are included in the experiment. The effect of adventitious water on the rate of the polymerization and the number-average molecular weight, Mn of the resulting polymer are discussed in the Supplemental Material.

Fire and Gas Barrier Properties of Poly(styrene-co-acrylonitrile) Nanocomposites Using Polycaprolactone/Clay Nanohybrid Based-Masterbatch

Exfoliated nanocomposites are prepared by dispersion of poly(ε-caprolactone) (PCL) grafted montmorillonite nanohybrids used as masterbatches in poly(styrene-co-acrylonitrile) (SAN). The PCL-grafted clay nanohybrids with high inorganic content are synthesized by in situ intercalative ring-opening polymerization ofε-caprolactone between silicate layers organomodified by alkylammonium cations bearing two hydroxyl functions. The polymerization is initiated by tin alcoholate species derived from the exchange reaction of tin(II) bis(2-ethylhexanoate) with the hydroxyl groups borne by the ammonium cations that organomodified the clay. These highly filled PCL nanocomposites (25 wt% in inorganics) are dispersed as masterbatches in commercial poly(styrene-co-acrylonitrile) by melt blending. SAN-based nanocomposites containing 3 wt% of inorganics are accordingly prepared. The direct blend of SAN/organomodified clay is also prepared for sake of comparison. The clay dispersion is characterized by wide-angle X-ray diffraction (WAXD), atomic force microscopy (AFM), and solid state NMR spectroscopy measurements. The thermal properties are studied by thermogravimetric analysis. The flame retardancy and gas barrier resistance properties of nanocomposites are discussed both as a function of the clay dispersion and of the matrix/clay interaction.

Surface-initiated ring-opening polymerization of p-dioxanone on Wang resin bead

Biodegradable poly(p-dioxanone) (PPDO) was formed on Wang resin surface by surface-initiated ring-opening polymerization (SI-ROP). The SI-ROP of p-dioxanone (PDO) was achieved by heating a mixture of Tin(II) bis(2-ethylhexanoate) [Sn(Oct)2], hydroxyl functionalized Wang resin, and PDO in anhydrous toluene at 80 °C. The resultant polymer-grafted Wang resin (Wang-g-PPDO) was characterized by fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), optical microscopy (OM), and field-emission scanning electron microscopy (FE-SEM). The FTIR spectra of Wang-g-PPDO show peak characteristic of PPDO at 2943 cm−1 (CH stretch), at 1741 cm−1 (CO stretch), and 1136 cm−1 (COC stretch) indicating the formation of ester linkage between PPDO and hydroxyl terminated Wang resin. The DSC thermogram show melting peak corresponding to PPDO polymer on Wang resin surface. Thermogravimetric investigation shows increase in PPDO content on the Wang resin surface in terms of percentage of weight loss with increase in reaction time. The OM and SEM photographs clearly show the formation of PPDO polymer on the Wang resin surface without altering the spherical nature of Wang resin bead. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1178–1184, 2008

SnO2가 도핑된 TiO2박막의 합성 및 광촉매 효과

SnO₂-doped TiO₂ thin films were prepared from tin (IV) bis (acetylacetonate) dichloride and titanium diisopropoxide bis (acetylacetonate) with pluronic P123 or degussa P25 as a structural-directing agent. These hydrolyzed sol were spin coated onto Si(100) wafer substrate. The microstructure, morphology and bonding states of thin films were studied by field-emission scanning electron microscopy (FE-SEM), X-ray diffractometry (XRD), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of these films was investigated by using indigo carmine solution.

Kinetics and mechanism of ɛ-caprolactone and l, l-lactide polymerization coinitiated with zinc octoate or aluminum acetylacetonate: The next proofs for the general alkoxide mechanism and synthetic applications

Following our previous papers on mechanism of cyclic esters' polymerization coinitiated by tin(II) octoate [tin(II) bis-(2-ethylhexanoate), (Sn(Oct) 2)] in the presence of either the low molar mass coinitiator (an alcohol, hydroxy acid, or H 2O) or a macromolecule fitted with a hydroxy end group (ROH), the present work deals with ɛ-caprolactone (CL) and l, l-lactide (LA) polymerizations coinitiated with zinc octoate (Zn(Oct) 2) or aluminum acetylacetonate (Al(Acac) 3). A series of kinetic measurements revealed that similarly as in the Sn(Oct) 2 coinitiated process, these polymerizations proceed by simple monomer insertion into the …Mt–OR bond, reversibly formed in the reaction –Mt–L + ROH ⇌ …–Mt–OR + LH (where Mt = Sn, Zn or Al; L = Oct or Acac), taking place throughout the whole polymerization process. MtL n itself does not play an active role in the polymerization. Applicability of the commercially available Zn(Oct) 2 or Al(Acac) 3 for the aliphatic polyester (10 3 ≤ M n ≤ 4 × 10 5) synthesis is also discussed.

Thin organic layers prepared by MAPLE for gas sensor application

It was shown that organic materials can be used as an active layer for conductivity gas sensors. It was found that Pulse Laser Deposition (PLD) is a convenient technology for producing thin layers (from nanometers to micrometers). Metal Acetylacetonates (MAcAc) exhibit high sensitivity to oxidizing gases as well as reducing atmospheres. New technology—MAPLE—Matrix Assisted Pulse Laser Deposition has been previously developed for deposition of thin films from large organic molecules (up to several hundreds of amu). Starting material is embedded in frozen matrix, which plays important role during energy transfer while laser pulse hits the target. First experiments have been done with Indium (III) acetylacetonate and Tin(IV) bis(acetylacetonate) dichloride. To certify successful transfer of original material FTIR and SEM analyses have been used. Gas sensors with those layers were tested at different atmospheres and temperature dependent sensitivity was acquired. Results from DC measurements show, that MAPLE technology is the very perspective for preparation of high demand gas sensors.

Kinetics and Mechanism of Cyclic Esters Polymerization Initiated with Tin(II) Octoate. Polymerization of ε-Caprolactone and l,l-Lactide Co-initiated with Primary Amines

Following our previous papers on the mechanism of ε-caprolactone (CL) and l,l-lactide (LA) polymerization initiated by tin(II) octoate [(tin(II) bis(2-ethylhexanoate), (Sn(Oct)2)] in the presence of the hydroxyl-group-containing compounds [H2O, alcohols or hydroxy-carboxylic acids (ROH)] the present work shows that the CL or LA/Sn(Oct)2/primary amine (RNH2) system, in principle, does not differ mechanistically from the CL or LA/Sn(Oct)2/ROH system. 1H NMR, matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) mass spectrometric and kinetic studies reveal that, in the first step of polymerization initiated with the Sn(Oct)2/RNH2 mixtures, formation of the α-amido-ω-alcohol (RNH-m-H (R‘OH)) (in which m denotes the repeating unit derived from CL or LA) proceeds. Then, the further steps of polymerization follow with R‘OH as co-initiator. Thus, eventually, the Sn(Oct)2/RNH2-initiated polymerization proceeds by the monomer insertion into the ...-Sn−OR‘ ‘ bond, reversibly formed in the reaction: ...-SnOct + R‘ ‘OH ⇌ ...-Sn−OR‘ ‘ + OctH, in which R‘ ‘OH is either the low-molar-mass co-initiator (R‘OH) or a macromolecule fitted with the hydroxyl end group (RNH-(m)n-H); OctH stands for 2-ethylhexanoic (octanoic) acid. These interconversions take place throughout the entire polymerization process. The Sn(Oct)2/amino dendrimer (e.g., commercially available DAB−Am-8 and DAB−Am-32, polyamines, fitted with 8 and 32 primary amino groups) system acts in a similar way. Molar masses of the resulting star-shaped polymer, in which polyester chains bear the hydroxyl end groups, are controlled by the monomer and dendrimer concentrations ratio in the feed.