The living ring-opening polymerization of δ-valerolactone (VL) initiated from 6-azide-1-hexanol using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1-[3,5-bis(trifluoromethyl)phenyl]-3-cyclohexylthiourea (BCT) was carried out to prepare the poly(δ-valerolactone)s (N 3 -PVL-OH) bearing azide groups at the R-chain ends with M n,NMR s (PDIs) of 2600 (1.08), 4700 (1.11), and 9900 (1.09). The acetylene functionality was introduced at the ω-end of N 3 -PVL-OH using 5-hexynoyl chloride to afford the telechelic poly(δ-valerolactone) with the azide group at the R-end and acetylene group at the ω-end (N 3 -PVL-CtCH). The click reaction between the R-azide and the ω-acetylene of N 3 -PVL-CtCH in DMF was carried out under the highly diluted condition as [N 3 -PVL-CtCH] = 0.18 mM, which was monitored by IR and 1 H NMR measurements. The SEC peak of the cyclic-PVL shifted to the lower molecular weight region than that of N 3 -PVL-CtCH, and the intrinsic viscosity of the cyclic-PVL significantly decreased. In addition, there was no change in the molecular weight of the resulting polymer through the click cyclization, which was confirmed on the basis of the MALDI-TOF MS measurement. Finally, we succeeded in the synthesis of a well-defined cyclic-PVL having a narrow polydispersity (M w /M n = 1.09-1.15) and the predicted molecular weight (M n,NMR = 2800-9500) in reasonable yield (60-80%) using the click cyclization.

For the living ring‐opening polymerization (ROP) of epoxy monomers, the catalytic activity of organic superbases, tert‐butylimino‐tris(dimethylamino)phosphorane, 1‐tert‐butyl‐2,2,4,4,4‐pentakis(dimethylamino)‐2Λ5,4Λ5‐catenadi(phosphazene), 2,8,9‐triisobutyl‐2,5,8,9‐tetraaza‐1‐phosphabicyclo[3.3.3]undecane, and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris(dimethylamino)phosphoranylidenamino]‐2Λ5,4Λ5‐catenadi(phosphazene) (t‐Bu‐P4), was confirmed. Among these superbases, only t‐Bu‐P4 showed catalytic activity for the ROP of 1,2‐butylene oxide (BO) to afford poly(1,2‐butylene oxide) (PBO) with predicted molecular weight and narrow molecular weight distribution. The results of the kinetic, post‐polymerization experiments, and MALDI‐TOF MS measurement revealed that the t‐Bu‐P4‐catalyzed ROP of BO proceeded in a living manner in which the alcohol acted as the initiator. This alcohol/t‐Bu‐P4 system was applicable to the glycidol derivatives, such as benzyl glycidyl ether (BnGE) and t‐butyl glycidyl ether, to afford well‐defined protected polyglycidols. The α‐functionalized polyethers could be obtained using different functionalized initiators, such as 4‐vinylbenzyl alcohol, 5‐hexen‐1‐ol, and 6‐azide‐1‐hexanol. In addition, the well‐defined cyclic‐PBO and PBnGE were successfully synthesized using the combination of t‐Bu‐P4‐catalyzed ROP and click cyclization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

The ring-opening polymerization (ROP) of styrene oxide (SO) was carried out using 3-phenyl-1-propanol (PPA) as the initiator and a phosphazene base, 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phosphoranylidenamino]-2Λ5,4Λ5-catenadi(phosphazene) (t-Bu-P4), as the catalyst at room temperature. The polymerization proceeded in a living manner, which was confirmed by the kinetic and chain extension experiments, to produce the poly(styrene oxide) (PSO) with a controlled molecular weight (5200–21 800 g mol–1) and narrow molecular weight distribution (<1.14). The 1H NMR and MALDI-TOF MS measurements of the obtained PSO clearly indicated the presence of the PPA residue at the chain end. In addition, the t-Bu-P4-catalyzed ROP of SO with functional initiators, such as 4-vinylbenzyl alcohol, 5-hexen-1-ol, 6-azide-1-hexanol, and 3-hydroxymethyl-3-methyloxetane, successfully afforded the corresponding end-functionalized PSO with precise molecular control. The t-Bu-P4-catalyzed ROP of SO proceeded through the β- and α-scissions as the main and minor ring-opening manners on the basis of the microstructure of the PSOs analyzed by the 13C NMR measurement, which was clarified in the model reactions corresponding to the initiation and propagation. For the thermal analysis of PSO, the glass transition temperature and 5% weight loss temperature were found to be 34 and 310 °C, respectively.

Low‐temperature anionic ring‐opening homopolymerizations and copolymerizations of two glycidol derivatives (allyl glycidyl ether (AGE) and ethoxyethyl glycidyl ether (EEGE)) are studied using a metal‐free catalyst system, 3‐phenyl‐1‐propanol (PPA) (an initiator) and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris‐(dimethylamino)phosphoranylidenamino]‐2Λ5,4Λ5‐catenadi(phosphazene) (t‐Bu‐P4) (a promoter) in order to obtain well‐defined functional linear polyethers and diblock copolymers. With the aid of the catalyst system, AGE is found to successfully undergo anionic ring‐opening polymerization (ROP) even at room temperature (low reaction temperature) without any side reactions, producing well‐defined linear AGE‐homopolymer in a unimodal narrow molecular weight distribution. Under the same conditions, EEGE also undergoes polymerization, producing a linear EEGE‐homopolymer in a unimodal narrow molecular‐weight distribution. In this case, however, a side reaction (i.e., chain‐transfer reaction) is found to occur at low levels during the early stages of polymerization. The chemical properties of the monomers in the context of the homopolymerization reactions are considered in the design of a protocol used to synthesize well‐defined linear diblock copolyethers with a variety of compositions. The approach, anionic polymerization via the sequential step feed of AGE and EEGE as the first and second monomers, is found to be free from side reactions at room temperature. Each block of the obtained linear diblock copolymers undergoes selective deprotection to permit further chemical modification for selective functionalization. In addition, thermal properties and structures of the polymers and their post‐modification products are examined. Overall, this study demonstrates that a low‐temperature metal‐free anionic ROP using the PPA/t‐Bu‐P4 catalyst system is suitable for the production of well‐defined linear AGE‐homopolymers and their diblock copolymers with the EEGE monomer, which are versatile and selectively functionalizable linear aliphatic polyether platforms for a variety of post‐modifications, nanostructures, and their applications.

The cationic ring‐opening multibranching polymerization of 2‐hydroxymethyloxetane (1) as a novel latent AB2‐type monomer was carried out using trifluoromethane sulfonic acid or trifluoroboron diethyl etherate by a slow‐monomer‐addition (SMA) method. The polymer yield of poly‐1 ranged from ca. 58–88%, which increase with the increasing monomer addition time on the SMA method. The absolute molecular weights (Mw,MALLS) and the polydispersities of poly‐1 were in the range of 8,000–43,500 and 1.45–4.53, respectively, which also increased with the increasing monomer addition time. The Mark‐Houwink‐Sakurada exponents α in 0.2 M NaNO3 aq. were determined to be 0.02–0.25 for poly‐1, indicating that poly‐1 has compact forms in the solution because of the highly branched structure. The degree of the branching value of poly‐1, which was calculated by Frey's equation, ranged from ca. 0.50 to 0.58, which increased with the increasing monomer addition time. The steady shear flow of poly‐1 in aqueous solution exhibited a Newtonian behavior with steady shear viscosities independent of the shear rate. The results of the MALLS, NMR, and viscosity measurements indicated that poly‐1 is composed of a highly branched structure, i.e., the hyperbranched poly (2‐hydroxymethyloxetane). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011