PCL Triblock Copolymer Research Articles

PEGylated cationic nanoassemblies based on triblock copolymers to combine siRNA therapeutics with anticancer drugs.

Nowadays, the clinical administration of siRNA therapeutics is still challenging due to the need of safe and efficient delivery carriers. In this context, biodegradable and amphiphilic triblock copolymers (ABC) containing amine-based cationic segments could be a powerful tool for siRNA delivery. Herein, we propose a range of poly(ethylene glycol) (PEG)-poly(2-dimethyl(aminoethyl) methacrylate) (pDMAEMA)-polycaprolactone (PCL) copolymers with different lengths of the blocks and hydrophilic/lipophilic balance to deliver siRNA alone or in association with a conventional anticancer drug. mPEG-pDMAEMA-PCL copolymers were synthesized by a combination of techniques and characterized by NMR analysis, Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). Copolymers were then employed to prepare NPs through nanoprecipitation. NPs based on copolymers with long PCL chains (SSL-NPs and LLL-NPs) showed the best colloidal properties and a highly stable core-shell structure with a better orientation of the PEG fringe on the surface. Concerning siRNA delivery, SSL-NPs based on copolymers with short PEG and pDMAEMA chains showed optimized ability to complex and then deliver siRNA at the cell level. The strong interaction between the nucleic acid and the cationic pDMAEMA blocks of NPs was then confirmed by release studies that showed a sustained release of siRNA within 48 h. The transfection efficiency of NPs was assessed in human melanoma cells. NPs were complexed with a therapeutic siRNA against TUBB3 (TUB-siRNA). We observed the best results with SSL-NPs, probably due to the higher preserved buffer capacity of the pDMAEMA blocks. Finally, in order to give a proof of concept of a possible application in the combined chemo/gene-therapy of cancer, SSL-NPs complexed with TUB-siRNA were loaded with docetaxel (DTX) and then cytotoxicity was evaluated in the same cell line. The co-delivery of TUB-siRNA into NPs appeared to strongly potentiate the anti-proliferative activity of DTX, thus highlighting the combinatory activity of the NPs.

Synthesis of PCL–PEG–PCL Triblock Copolymer via Organocatalytic Ring-Opening Polymerization and Its Application as an Injectable Hydrogel—An Interdisciplinary Learning Trial

Biocompatible and biodegradable block copolymers composed of poly(ethylene glycol) (PEG) and aliphatic polyester are a class of promising biomaterials. Herein, a teaching experiment was designed to furnish undergraduates with a reliable method to synthesize an amphiphilic poly(e-caprolactone)-PEG-poly(e-caprolactone) (PCL–PEG–PCL) triblock copolymer via ring-opening polymerization of e-caprolactone using PEG as the macroinitiator and diphenyl phosphate as the green organocatalyst; the concentrated solution of synthetic polymer in water was then demonstrated as an injectable thermogel with a sol–gel transition upon heating. Ten students serving as volunteers successfully synthesized PCL–PEG–PCL copolymer, and then analyzed their specimens using various techniques including proton-nuclear magnetic resonance spectroscopy, gel permeation chromatography, differential scanning calorimetry, and X-ray diffraction and learned the principles of instruments. Finally, students prepared an aqueous polymer solution, and observed its interesting spontaneous physical gelation upon heating via the tube-inverting approach and dynamic rheological analysis. The experimental features captured the students’ attention and made them more enthusiastic participants. This newly designed teaching experiment afforded senior undergraduates an excellent opportunity to consolidate basic concepts and principles in books with practical experimental sessions in the field of polymer chemistry, analytical chemistry, and materials science.

New, Environment Friendly Approach for Synthesis of Amphiphilic PCL–PEG–PCL Triblock Copolymer: An Efficient Carrier for Fabrication of Nanomicelles

Ring opening copolymerization is the most frequently applied reaction for the synthesis of polycaprolactone–polyethylene glycol–polycaprolactone (PCL–PEG–PCL). In this reaction, a number of expensive and toxic organic solvents are being used for the purpose of purification and extraction of the prepared copolymer. Exposure to these organic solvents can cause serious issues to the human health and also impart serious environmental pollution. In the current work, a new, economical and organic solvent free approach was used for the synthesis of triblock copolymer. The results of the current studies confirmed the successful formation of triblock copolymer as revealed by Fourier transform infrared spectra, 13carbon nuclear magnetic resonance (13C-NMR) and proton nuclear magnetic resonance (1H-NMR). Gel permeation chromatography analysis ensured the homo-distribution of the prepared copolymer. The prepared copolymer was further evaluated as a carrier for the drug loading. Nanomicelles were successfully prepared by the nanoprecipitation technique and exhibited an average size distribution of 42.50 nm and an encapsulation efficiency of 90%. The prepared nanomicelles also exhibited safety at the concentration of 50 µg/ml and a long-term storage stability. All these studies suggested the success of the new simplest and economical method for the synthesis of PCL–PEG–PCL and its subsequent applications as a carrier for fabrication and efficient delivery of hydrophobic drug molecules.

Preparation and evaluation of PCL–PEG–PCL polymeric nanoparticles for doxorubicin delivery against breast cancer

DOX-loaded polymeric NPs based on PCL–PEG–PCL triblock copolymers were successfully prepared and showed highly efficient targeting and accumulation in tumor via EPR effect. The prepared NPs would be a promising nanosized DDS for cancer therapy.

Nanostructured epoxy thermoset templated by an amphiphilic PCL-b -PES-b -PCL triblock copolymer

Nanostructured epoxy thermoset templated by an amphiphilic PCL-<i>b</i> -PES-<i>b</i> -PCL triblock copolymer

Hydrogen bonding interactions in poly(ε-caprolactone–dimethyl siloxane–ε-caprolactone)/poly(hydroxyether of bisphenol A) triblock copolymer/homopolymer blends and the effect on crystallization, microphase separation and self-assembly

This study investigated the self-assembled microphase separated morphologies that are obtained in bulk, by the complexation of a semicrystalline poly(ε-caprolactone–dimethyl siloxane–ε-caprolactone) (PCL–PDMS–PCL) triblock copolymer and a homopolymer, poly(hydroxyether of bisphenol A) (PH) in tetrahydrofuran (THF). In these blends, microphase separation takes place due to the disparity in intermolecular interactions; specifically, the homopolymer interacts with PCL blocks through hydrogen bonding interactions. The crystallization, microphase separation and crystalline structures of a triblock copolymer/homopolymer blends were investigated. The phase behavior of the complexes was investigated using small-angle X-ray scattering and transmission electron microscopy. At low PH concentrations, PCL interacts relatively weakly with PH, whereas in complexes containing more than 50wt% PH, the PCL block interacts significantly with PH, leading to the formation of composition-dependent nanostructures. SAXS and TEM results indicate that the lamellar morphology of neat PCL–PDMS–PCL triblock copolymer changes into disordered structures at 40–60wt% PH. Spherical microdomains were obtained in the order of 40–50nm in complexes with 80wt% PH. At this concentration, the complexes show a completely homogenous phase of PH/PCL, with phase-separated spherical PDMS domains. The formation of these nanostructures and changes in morphology depends on the strength of hydrogen bonding between PH/PCL blocks and also the phase separated PDMS blocks.

Comparative studies of thermogels in preventing post-operative adhesions and corresponding mechanisms.

Post-surgical peritoneal adhesions constitute a classic problem in surgery, and thus anti-adhesion materials are much required. In this study, a series of polyester-PEG-polyester triblock copolymers with different biodegradable polyester compositions were synthesized, their properties were examined, and the in vivo efficacies as anti-adhesion biomaterials were evaluated in a comparative way for the first time. These samples not only exhibited various morphologies in the bulk state, but also possessed different stabilities in the sol state. All the polymer aqueous solutions with appropriate compositions and concentrations underwent sol-gel transitions with increase of temperature and formed semi-solid hydrogels at body temperature. The efficacy of PEG/polyester thermogels (25 wt%) for preventing post-operative abdominal adhesions was investigated and compared in a rabbit model of sidewall defect-bowel abrasion. Different efficacies of anti-adhesion were observed, possible mechanisms were discussed, and the importance of viscoelasticity was suggested for the first time. These results illustrated that appropriate properties of PEG/polyester thermogels including viscoelastic matrix, hydrophilic surface and moderate in vivo persistence played crucial roles in enabling an effective device to prevent post-surgical peritoneal adhesions.

Preparation of injectable and thermoresponsive hydrogel based on penta-block copolymer with improved sol stability and mechanical properties

New biocompatible, biodegradable and thermosensitive penta-block copolymer poly (N-isopropylacrylamide)–b-poly (∊-caprolactone)–b-poly ethylene glycol–b-poly (∊-caprolactone)–b-poly (N-isopropylacrylamide) (PNIPAAm–PCL–PEG–PCL–PNIPAAm) was synthesized by a combination of controlled ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). This penta-block copolymer undergoes reversible sol–gel transitions between room temperature (22 °C) and human body temperature (37 °C). By incorporation of poly (N-isopropylacrylamide) (PNIPAAm) block at the end of PCL–PEG–PCL (PCEC) triblock copolymer, the resulting PNIPAAm–PCEC–PNIPAAm penta-block copolymer achieves improved mechanical properties and high sol stability while keeping its thermogelling property in the range of physiological temperatures 20–50 °C. The mechanical properties of these materials as a function of temperature were measured by rheometry. To confirm the sol stability, the crystalizability of penta-block copolymer was analyzed by the XRD. The sol-to-gel transition temperature of block copolymer aqueous solution is controllable by varying the composition and molecular weight of PEG and PNIPAAm. Their physicochemical properties in aqueous media were characterized by 1H NMR spectroscopy and GPC techniques. This amphiphilic copolymer is self-assembled into spherical micelles in aqueous solution at room temperature. The critical micelle concentration (CMC) of these amphiphilic block copolymers was studied by fluorescence techniques. The size distribution and thermal responses of the polymeric micelles and aggregation to hydrogel in higher temperature were investigated by dynamic light scattering (DLS). The synthesized copolymer showed no apparent cytotoxicity on normal cells. In vitro release studies showed that the anticancer agent Na-HCl is effectively loaded and released by the temperature sensitive PNIPAAm–PCEC–PNIPAAm penta-block copolymer.

Hydrogen bonding interactions, crystallization, and surface hydrophobicity in nanostructured epoxy/block copolymer blends

AbstractHydrogen bonding interactions, phase behavior, crystallization, and surface hydrophobicity in nanostructured blend of bisphenol A‐type epoxy resin (ER), for example, diglycidyl ether of bisphenol A (DGEBA) and poly(ε‐caprolactone)‐block‐poly(dimethyl siloxane)‐block‐poly(ε‐caprolactone) (PCL–PDMS–PCL) triblock copolymer were investigated by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, transmission electron microscopy, small‐angle X‐ray scattering, and contact angle measurements. The PCL–PDMS–PCL triblock copolymer consisted of two epoxy‐miscible PCL blocks and an epoxy‐immiscible PDMS block. The cured ER/PCL–PDMS–PCL blends showed composition‐dependent nanostructures from spherical and worm‐like microdomains to lamellar morphology. FTIR study revealed the existence of hydrogen bonding interactions between the PCL blocks and the cured epoxy, which was responsible for their miscibility. The overall crystallization rate of the PCL blocks in the blend decreased remarkably with increasing ER content, whereas the melting point was slightly depressed in the blends. The surface hydrophobicity of the cured ER increased upon addition of the block copolymer, whereas the surface free energy (γs) values decreased with increasing block copolymer concentration. The hydrophilicity of the epoxy could be reduced through blending with the PCL–PDMS–PCL block copolymer that contained a hydrophobic PDMS block. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 790–800, 2010

Biodegradable in situ gel-forming controlled drug delivery system based on thermosensitive PCL–PEG–PCL hydrogel: Part 1—synthesis, characterization, and acute toxicity evaluation

In this work, biodegradable PCL–PEG–PCL (PCEC) triblock copolymers were successfully synthesized at one-step. Aqueous solution of PCEC copolymer displayed thermosensitive sol–gel–sol transition behavior, which is flowing sol at low temperature and turns into non-flowing gel at body temperature. The cytotoxicity of PCEC copolymer was evaluated by cell viability assay using HEK293 and WISH cells. In vivo gel-formation, degradation test, acute toxicity tests, and histopathological study of PCEC hydrogels were performed in BALB/c mice by subcutaneous administration. In acute toxicity test, the mice were observed continuously for 21 days. For histopathologic study, samples including heart, liver, spleen, lung, kidneys, and tissue of injection site were histochemical prepared and stained with hematoxylin–eosin. No mortality or significant signs of acute toxicity was observed during the whole observation period and there is no significant lesion to be shown in histopathologic study of major organs and tissue of injection site. The maximum tolerance dose (MTD) of PCEC hydrogel (20 wt%) by subcutaneous administration was calculated to be higher than 25 g/kg b.w. The results indicated that the obtained PCEC hydrogel was non-toxic after subcutaneous administration, and could be a safe candidate for in situ gel-forming controlled drug delivery system. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4684–4694, 2009

Effect of temperature and water on microphase separation of PCL–PEO–PCL triblock copolymers

Microphase separation of poly(e-caprolactone-ethylene oxide-e-caprolactone) (PCL–PEO–PCL), with block number-average molecular weights of 9,100–30,400–9,100 g/mol, was studied. Cylindrical morphology was observed in a solvent-cast sample. When the as-cast sample was heated above the melting points of both PEO and PCL blocks, a change in morphology was observed by Small Angle X-ray Scattering (SAXS). When this sample was cooled to room temperature in the ambient atmosphere, another morphology (lamellae) was observed with SAXS and Atomic Force Microscopy (AFM). This asymmetric change in morphology suggests a role of kinetics (microphase separation and crystallization) in determining the observed microstructures. Addition of water at room temperature also affected microphase separation of the block copolymer due to hydrophilicity of PEO. As the polymer concentration decreases from 100 to 60%, the morphology changes from cylinders to lamellae. Differential Scanning Calorimetry (DSC) data show that water addition decreases PEO crystallinity but PCL crystallinity remains.

Ring-opening polymerization of ɛ-caprolactone by poly(propyleneglycol) in the presence of a monomer activator

The ring-opening polymerization of ɛ-caprolactone (CL) was induced by using polypropylene glycol (PPG) as an initiator in the presence of the monomer activator HCl·Et 2O to synthesize triblock copolymers composed of PPG and poly(ɛ-caprolactone) (PCL). The degree of CL conversion and the molecular weight of PCL increased linearly with the polymerization time or with the feed ratio of CL to PPG in the presence of HCl·Et 2O in CH 2Cl 2 at 25 °C. The PCLs obtained had molecular weights close to the theoretical values calculated from the CL:PPG molar ratios and exhibited monomodal GPC curves with narrow polydispersity indexes. The apparent rate constant ( k app) for the polymerization of CL activated by HCl·Et 2O was greatly affected by the ratio of HCl·Et 2O/PPG. The activation energy for the polymerization of CL in this system was estimated to be 49.8 kJ/mol K. We successfully prepared PPG and PCL triblock copolymers using this activated monomer mechanism.

Lipase Catalyzed Synthesis of Poly(ε-Caprolactone)−Poly(Dimethylsiloxane)−Poly(ε-Caprolactone) Triblock Copolymers

Immobilized lipase B from Candida antarctica was used to synthesize copolymers of poly(e-caprolactone) (PCL) with α,ω-(dihydroxy alkyl) terminated poly(dimethylsiloxane) (PDMS). The reactions were carried out in toluene with a 1:2 w/v ratio of the monomers to solvent at 70 oC. The PCL−PDMS−PCL triblock copolymer composition was varied by changing the feed ratio of the reactants [CL]/[PDMS] (80:20; 60:40; 40:60; 20:80 w/w, respectively). The enzymatically synthesized copolymers were characterized by GPC, FTIR, TGA, DSC and XRD. The successful synthesis of the copolymers was confirmed by the appearance of a single peak in all of the respective GPC chromatograms. An increased feed ratio of [CL]/[PDMS] produced an increase in the number-average molecular weight (Mn) of the copolymers from 4,400 g mol−1 (20:80 w/w of [CL]/[PDMS]) to 13,950 g mol−1 (80:20 w/w of [CL]/[PDMS]). The copolymers were shown by DSC and XRD to be semi-crystalline and the degree of crystallinity increased with an increase in the [CL]/[PDMS] feed ratio. The crystal structure in the copolymers was analogous to that of the PCL homopolymer. In enzymatic polymerization the recovery and reuse of the enzyme is highly desirable. When the lipase was recovered and reused for the copolymerization, higher molecular weight copolymers were obtained upon a second use. This appears to be due to an increased activity of the immobilized lipase following an opening up of the acrylic resin matrix in the organic medium. This improvement was not maintained for subsequent recycling of the lipase principally due to the disintegration of the acrylic resin matrix.

Synthesis of Thermo-Sensitive Micellar Aggregates Self-Assembled from Biotinylated PNAS-b-PNIPAAm-b-PCL Triblock Copolymers for Tumor Targeting

The stimuli-sensitive diblock copolymer poly(N-acroyloxysuccinimide)-b-poly(N-isopropylacrylamide) (PNAS-b-PNIPAAm) was synthesized via reversible addition−fragmentation chain transfer (RAFT) polymerization. By using the terminal carboxyl group of the diblock copolymer to initiate the ring-opening polymerization of e-caprolactone (CL), the amphiphilic PNAS-b-PNIPAAm-b-PCL triblock copolymer was further synthesized. The triblock copolymer was characterized by NMR, IR, and SEC-MALLS. To enhance the internalization to tumor cells, biotin was introduced into the triblock copolymer. The LCST of biotinylated PNAS-b-PNIPAAm-b-PCL was about 35.3 °C. The formation of micellar aggregates (MAs) self-assembled from biotinylated PNAS-b-PNIPAAm-b-PCL was confirmed by CMC and TEM. The cell viability study demonstrated that the MAs have a low cytotoxicity. The antitumor drug doxorubicin (Dox) was loaded in the MAs, and in vitro release behavior of Dox showed the MAs exhibited thermo-sensitive drug release. The confocal m...

Synthesis of Novel Linear PEO‐b‐PS‐b‐PCL Triblock Copolymers by the Combination of ATRP, ROP, and a Click Reaction

AbstractA new strategy to synthesize a series of well‐defined amphiphilic PEO‐b‐PS‐b‐PCL block copolymers is presented. First, bromine‐terminated diblock copolymers PEO‐b‐PS‐Br are prepared by ATRP of styrene, and converted into azido‐terminated PEO‐b‐PS‐N3 diblock copolymers. Then propargyl‐terminated PCL is prepared by ROP of ε‐caprolactone. The PEO‐b‐PS‐b‐PCL triblock copolymers with $\overline M _{\rm n}$ from 1.62 × 104 to 1.96 × 104 and a narrow PDI from 1.09 to 1.19 are finally synthesized from these precursors. The structures of these triblock copolymers and their precursors have been characterized by NMR, IR, and GPC analysis.magnified image

Enzymatic degradation of block copolymers obtained by sequential ring opening polymerization of l-lactide and ɛ-caprolactone

Copolymers of ɛ-caprolactone and l-lactide with different molar ratios were prepared via sequential ring opening polymerization (ROP) of both monomers. The resulting PCL–PLLA–PCL triblock copolymers were characterized by using NMR, SEC, DSC and XRD. One melting peak corresponding to the PCL block was detected, but the presence of PLLA decreased the crystallinity of PCL. Enzyme-catalyzed biodegradation of solution cast films was investigated at 37 °C in the presence of Pseudomonas lipase. It was observed that the PLLA component retarded the degradation of the block copolymer as compared to the PCL homopolymer. Therefore, the enzymatic degradation rate can be adjusted by varying the composition of the copolymers. 1H NMR and SEC data showed no significant chemical composition or molecular weight changes during degradation, indicating that the degradation proceeded according to a surface erosion mechanism. ESEM confirmed surface erosion with appearance of a rugged morphology.

Synthesis and Characterization of Novel Hydroxyalkyl Carbamate and Dihydroxyalkyl Carbamate Terminated Poly(dimethylsiloxane) Oligomers and Their Block Copolymers with Poly(ε-caprolactone)

Novel hydroxyalkyl carbamate, dihydroxyalkyl carbamate terminated poly(dimethylsiloxane) (PDMS) oligomers, and carbamate-linked block copolymers with poly(e-caprolactone) (PCL) were designed, synthesized, and characterized using combinatorial and high-throughput experimentation (CHTE). Novel hydroxyalkyl carbamate terminated PDMS oligomers were synthesized by reacting 3-aminopropyl terminated PDMS oligomers with ethylene carbonate (EC); further reaction of these oligomers with e-caprolactone (e-CL) resulted in novel carbamate-linked PCL−PDMS−PCL triblock copolymers. Novel dihydroxyalkyl carbamate terminated PDMS oligomers were synthesized by reacting 3-aminopropyl terminated PDMS with glycerine carbonate (GC); further reaction of these oligomers with e-CL resulted in novel H-type block copolymers of PDMS and PCL. Structural characterization of the synthesized oligomers and block copolymers was carried out with high-throughput FTIR, DSC, and NMR. Molecular weights of the oligomers and block copolymers were...

Formation of lamellar structure by competition in crystallization of both components for crystalline–crystalline block copolymers

Crystallization and structure formation of poly(ethylene oxide)–poly(ɛ-caprolactone) block copolymers (PEG–PCL) in which the melting temperatures of the components are close to each other were elucidated using differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. The diblock copolymers with 33, 46 and 59 wt% of PEG composition formed ordinary single spherulites similar to those of PCL homopolymers, while concentric double-circled spherulites appeared for the PCL–PEG–PCL triblock copolymer with 66 wt% PEG composition as observed previously. For the diblock copolymers, despite of the ordinary appearance of the single spherulites, the DSC thermograms and the WAXD patterns indicated the crystallization of PEG as well as PCL. The time-resolved SAXS profiles for the diblock copolymers showed that long spacings of the crystal lamellae decreased stepwise in the crystallization process. Synthesizing these results for the single spherulites, it was concluded that PCL crystallized first followed by the crystallization of PEG with preservation of the PCL crystal lamellar structure. This means that PEG must crystallize within confined space between the formerly formed PCL crystal lamellae. Such confined crystallization of PEG caused the suppressed melting temperature, crystallinity and crystallization rate especially in the smaller PEG compositions. In the melting process of the diblock copolymers, it was observed that the PEG component first melted with a stepwise increase in the long spacing.

Library synthesis and characterization of 3‐aminopropyl‐terminated poly(dimethylsiloxane)s and poly(ϵ‐caprolactone)‐b‐poly(dimethylsiloxane)s

p 4884, right column, lines 17–18, section heading: Combinatorial Synthesis of APT–PDMS and PCL–PDMS–PCL Triblock Copolymers p 4887, left column, lines 7–10: Thus, the catalyst benzyltrimethylammonium hydroxide can be used for the synthesis of APT–PDMS oligomers over a broad range of molecular weights. p 4887, left column, line 32, section heading: Trial Library Synthesis of APT–PDMS These errors have been corrected in the online version of the article. Citations to the article should use the original volume, issue, and page numbers. We apologize for the errors and any inconvenience that they may have caused.

Library synthesis and characterization of 3‐aminopropyl‐terminated poly(dimethylsiloxane)s and poly(ϵ‐caprolactone)‐b‐poly(dimethylsiloxane)s

AbstractLibraries of 3‐aminopropyl‐terminated poly(dimethylsiloxane) (APT–PDMS) and poly(ϵ‐caprolactone)–poly(dimethylsiloxane)–poly(ϵ‐caprolactone) (PCL—PDMS–PCL) triblock copolymers were synthesized. Preliminary experiments were carried out to select an appropriate catalyst and route for the poly(dimethylsiloxane) synthesis, and trial experiments were conducted to verify the successful synthesis of the intended polymer compositions. Then, a series of APT–PDMS oligomers were synthesized with an automated combinatorial high‐throughput synthesis system to cover a molecular weight range of 2500–50,000 g/mol. Trial PCL—PDMS–PCL triblock copolymers were synthesized with the automated reactor system and characterized in detail with rapid gel permeation chromatography, high‐throughput Fourier transform infrared, nuclear magnetic resonance, and differential scanning calorimetry. Finally, two library synthesis experiments were carried out in which the lengths of both the poly(dimethylsiloxane) and poly(ϵ‐caprolactone) blocks in the PCL—PDMS–PCL triblock copolymers were varied. The results obtained from these experiments demonstrated that it was possible to synthesize libraries of well‐defined APT–PDMS oligomers and PCL—PDMS–PCL triblock copolymers with an automated high‐throughput system. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4880–4894, 2006