Nitroxide‐Mediated Polymerization of Bio‐Based Farnesene with a Functionalized Methacrylate

Farnesene (Far) is a bio‐based terpene monomer that is similar in structure to commercially used dienes like butadiene and isoprene. Nitroxide‐mediated polymerization (NMP) is adept for the polymerization of dienes, but not particularly effective at controlling the polymerization of methacrylates using commercial nitroxides. In this study, Far is statistically copolymerized with a functional methacrylate, glycidyl methacrylate (GMA), by NMP using N‐succinimidyl modified commercial BlocBuilder (NHS‐BB) initiator. Reactivity ratios are determined to be r _Far = 0.54 ± 0.04 and r _GMA = 0.24 ± 0.02. The ability of the poly(Far‐stat‐GMA) chains to reinitiate for chain extension with styrene showed a clear shift in molecular weight and monomodal distribution. Copolymerizations using a new alkoxyamine, Dispolreg 007 (D7), is explored as it is shown to homopolymerize methacrylates, but not yet reported for statistical copolymerizations. Bimodal molecular weight distributions are observed when an equimolar ratio of Far and GMA is copolymerized with D7 due to slow decomposition of the initiator, but chain ends are active as shown by successful chain extension with styrene. Both NHS‐BB and D7 initiators are used to synthesize poly[Far‐b‐(GMA‐stat‐Far)] and poly(Far‐b‐GMA) diblock copolymers. While the NHS‐BB initiated polymer chains have lower dispersity, D7 exhibits more linear polymerization kinetics and maintains more active chain ends.     

Nitroxide‐mediated radical copolymerization of methyl methacrylate controlled with a minimal amount of 9‐(4‐vinylbenzyl)‐9H‐carbazole

The controlled nitroxide‐mediated homopolymerization of 9‐(4‐vinylbenzyl)‐9H‐carbazole (VBK) and the copolymerization of methyl methacrylate (MMA) with varying amounts of VBK were accomplished by using 10 mol % {tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino} nitroxide relative to 2‐({tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino}oxy)‐2‐methylpropionic acid (BlocBuilder?) in dimethylformamide at temperatures from 80 to 125 °C. As little as 1 mol % of VBK in the feed was required to obtain a controlled copolymerization of an MMA/VBK mixture, resulting in a linear increase in molecular weight versus conversion with a narrow molecular weight distribution (M_w /M_n ≈ 1.3). Preferential incorporation of VBK into the copolymer was indicated by the MMA/VBK reactivity ratios determined: r_VBK = 2.7 ± 1.5 and r_MMA = 0.24 ± 0.14. The copolymers were found significantly “living” by performing subsequent chain extensions with a fresh batch of VBK and by ³¹P NMR spectroscopy analysis. VBK was found to be an effective controlling comonomer for NMP of MMA, and such low levels of VBK comonomer ensured transparency in the final copolymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis,characterization, and cross‐linking of a library of statistical copolymers based on 2‐“soy alkyl”‐2‐oxazoline and 2‐ethyl‐2‐oxazoline

The synthesis of statistical copolymers consisting of 2‐ethyl‐2‐oxazoline (EtOx) and 2‐“soy alkyl”‐2‐oxazoline (SoyOx) via a microwave‐assisted cationic ring‐opening polymerization procedure is described. The majority of the resulting copolymers revealed polydispersity indices below 1.30. The reactivity ratios (r_EtOx 1.4 ± 0.3; r_SoyOx = 1.7 ± 0.3) revealed a clustered monomer distribution throughout the polymer chains. The thermal and surface properties of the pEtOx‐stat‐SoyOx copolymers were analyzed before and after UV‐curing demonstrating the decreased chain mobility after cross‐linking. In addition, the cross‐linked materials showed shape‐persistent swelling upon absorption of water from the air, whereby as little as 5 mol % SoyOx was found to provide efficient cross‐linking. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5371,–5379, 2007     

Synthesis of a new monomer N′‐(β‐methacryloyloxyethyl)‐2‐pyrimidyl‐(p‐benzyloxycarbonyl)aminobenzenesulfonamide and its copolymerization with N‐phenyl maleimide

The new monomer N′‐(β‐methacryloyloxyethyl)‐2‐pyrimidyl‐(p‐benzyloxy‐ carbonyl)aminobenzenesulfonamide (MPBAS) (M₁) is synthesized using sulfadiazine as parent compound. It could be homopolymerized and copolymerized with N‐phenyl maleimide (NPMI) (M₂) by radical mechanism using AIBN as initiator at 60 °C in dimethylformamide. The new monomer MPBAS and polymers were identified by IR, element analysis and ¹H NMR in detail. The monomer reactivity ratios in copolymerization were determined by YBR method, and r₁ (MPBAS) = 2.39 ± 0.05, r₂ (NPMI) = 0.33 ± 0.02. In the presence of ammonium formate, benzyloxycarbonyl groups could be broken fluently from MPBAS segments of copolymer by catalytic transfer hydrogenation, and the copolymer with sulfadiazine side groups are recovered. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2548–2554, 2000     

Synthesis of biodegradable thermoplastic elastomers from ε‐caprolactone and lactide

This article reports the synthesis and the properties of novel thermoplastic elastomers of A‐B‐A type triblock copolymer structure, where the hard segment A is poly(l ‐lactide) (PLLA) and the soft segment B is poly(ε‐caprolactone‐stat‐d ,l ‐lactide) (P(CL‐stat‐DLLA)). The P(CL‐stat‐DLLA) block with DLLA content of 30 mol % was applied because of its amorphous nature and low glass transition temperature (T_g = approximately ?40 °C). Successive polymerization of l ‐lactide afforded PLLA‐block‐P(CL‐stat‐DLLA)‐block‐PLLAs, which exhibited melting temperature (T_m = approximately 150 °C) for the crystalline PLLA segments and still low T_g (approximately ?30 °C) of the soft segments. The triblock copolymers showed very high elongation at break up to approximately 2800% and elastic properties. The corresponding d ‐triblock copolymers, PDLA‐block‐P(CL‐stat‐DLLA)‐block‐PDLAs (PDLA = poly(d ‐lactide)) were also prepared with the same procedure using d ‐lactide in place of l ‐lactide. When the PLLA‐block‐P(CL‐stat‐DLLA)‐block‐PLLA was blended with PDLA‐block‐P(CL‐stat‐DLLA)‐block‐PDLA, stereocomplex crystals were formed to enhance their T_m as well as tensile properties. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 489–495     

Radical heterogeneous polymerization behavior of N‐methyl‐α‐fluoroacrylamide in benzene

The polymerization of N‐methyl‐α‐fluoroacrylamide (NMFAm) initiated with dimethyl 2,2′‐azobisisobutyrate (MAIB) in benzene was studied kinetically and with electron spin resonance. The polymerization proceeded heterogeneously with the highly efficient formation of long‐lived poly(NMFAm) radicals. The overall activation energy of the polymerization was 111 kJ/mol. The polymerization rate (R_p) at 50 °C is given by R_p = k[MAIB]^0.75±0.05 [NMFAm]^0.44±0.05. The concentration of the long‐lived polymer radical increased linearly with time. The formation rate (R_p?) of the long‐lived polymer radical at 50 °C is expressed by R_p? = k[MAIB]^1.0±0.1 [NMFAm]^0±0.1. The overall activation energy of the long‐lived radical formation was 128 kJ/mol, which agreed with the energy of initiation (129 kJ/mol), which was separately estimated. A comparison of R_p? with the initiation rate led to the conclusion that 1‐methoxycarbonyl‐1‐methylethyl radicals (primary radicals from MAIB), escaping from the solvent cage, were quantitatively converted into the long‐lived poly(NMFAm) radicals. Thus, this polymerization involves completely unimolecular termination due to polymer radical occlusion. ¹H NMR‐determined tacticities of resulting poly(NMFAm) were estimated to be rr = 0.34, mr = 0.48, and mm = 0.18. The copolymerization of NMFAm(M₁) and St(M₂) with MAIB at 50 °C in benzene gave monomer reactivity ratios of r₁ = 0.61 and r₂ = 1.79. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2196–2205, 2001     

Synthesis and characterization of a poly(N‐isopropylacrylamide) with β‐cyclodextrin as pendant groups

A novel linear poly(N‐isopropylacrylamide) (PNIPA) with β‐cylodextrin (β‐CD) moiety (PNIPA‐β‐CD) was synthesized by the conjugation of β‐CD carrying amino groups (EDA‐β‐CD) onto PNIPA with epoxy groups (P(NIPA‐co‐GMA), M_n = 3.86 × 10⁴), and the related reaction conditions are investigated. PNIPA‐β‐CD was characterized by means of IR, NMR and UV spectroscopes, element analysis, and differential scanning calorimetry (DSC). The number‐average molecular weight (M_n) and the β‐CD content of the obtained PNIPA‐β‐CD are 4.87 × 10⁴ and 18.8 wt %, respectively. PNIPA‐β‐CD can not only respond to temperature stimuli but also include guest molecules. Lower critical solution temperature (LCST) of aqueous PNIPA‐β‐CD solution is similar to that of PNIPA. The association constant (K_a) for PNIPA‐β‐CD with methyl orange (MO) is 2.4 × 10³ L mol^?1 at pH 1.4, which is comparable to that of EDA‐β‐CD (K_a = 2.9 × 10³ L mol^?1). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3516–3524, 2005     

Copolymerization of glycidyl methacrylate with alkyl acrylate monomers

A newer approach to obtaining acrylic thermoset polymers with adequate hydrophilicity required for various specific end uses is reported. Glycidyl methacrylate (GMA) was copolymerized with n-butyl acrylate (n-BA), isobutyl acrylate (i-BA), and 2-ethylhexyl acrylate (2-EHA) in bulk at 60°C. with benzoyl peroxide as free radical initiator. The copolymer composition was determined from the estimation of epoxy group. Reactivity ratios were calculated by the Yezrielev, Brokhina, and Roskin method. For copolymerization of GMA (M₁) with n-BA (M₂) the reactivity ratios were r₁ = 2.15 ± 0.14, r₂ = 0.12 ± 0.03; with i-BA (M₂) they were r₁ = 1.27 ± 0.06, r₂ = 0.33 ± 0.031; and with 2-EHA (M₂) they were r₁ = 2.32 ± 0.14, r₂ = 0.13 ± 0.009. The reactivity ratios were the measure of distribution of monomer units in a copolymer chain; the values obtained are compared and discussed.     

Controllable ring‐opening copolymerization of L‐lactide and (3S)‐benzyloxymethyl‐(6S)‐methyl‐morpholine‐2,5‐dione initiated by a biogenic compound creatinine acetate

Ring‐opening copolymerization (ROCP) of L ‐lactide (L ‐LA) and (3S)‐benzyloxymethyl‐(6S)‐methyl‐morpholine‐2,5‐dione [(3S, 6S)‐BMMD] initiated by creatinine acetate, a biogenic organic compound, was performed in the bulk at 130 °C. The copolymerization was well controlled as evidenced by that both the measured values of number‐average molecular weight (M_n,NMR(OH) and M_n,NMR(COOH)) and serine molar fraction (F_Bz.ser) of synthesized copolymers were close to the corresponding theoretical values; and that the higher isotacticity of synthesized copolymers (85–86%) and lower racemization degree of the ROCP. After removing O‐benzyls of the copolymers with Et₃SiH/Et₃N/CH₂Cl₂ under catalysis of PdCl₂, functional biodegradable copolymers of L ‐lactic acid (L ‐Lac) and L ‐Ser with designed molar fraction of serine (F_ser 1.35%, 3.57%, 5.41%), narrow molecular weight distribution (polydispersity index 1.10–1.36), and improved hydrophilicity (θ_stat 82.3–89.6°) were finally obtained. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

“Smart” poly(2‐(dimethylamino)ethyl methacrylate‐ran‐9‐(4‐vinylbenzyl)‐9H‐carbazole) copolymers synthesized by nitroxide mediated radical polymerization

A series of poly(2‐(dimethylamino)ethyl methacrylate‐ran‐9‐(4‐vinylbenzyl)‐9H‐carbazole) (poly(DMAEMA‐ran‐VBK)) random copolymers, with VBK molar feed compositions f_VBK,0 = 0.02–0.09, were synthesized using 10 mol % [tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino] nitroxide (SG1) relative to 2‐([tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino]oxy)‐2‐methylpropionic acid (BlocBuilder) at 80 °C and 90 °C. Controlled polymerizations were observed, even with f_VBK,0 = 0.02, as reflected by a linear increase in number average molecular weight (M_n) versus conversion X ≤ 0.6 with final copolymers characterized by relatively narrow, monomodal molecular weight distributions (M_w/M_n ≈ 1.5). Poly(DMAEMA‐ran‐VBK) copolymers were deemed sufficiently pseudo‐“living” to reinitiate a second batch of N,N‐dimethylacrylamide (DMAA), with very few apparent dead chains, as indicated by the monomodal shift in the gel permeation chromatography chromatograms. Poly(DMAEMA‐ran‐VBK) random copolymers exhibited tuneable lower critical solution temperature (LCST), in aqueous solution, by modifying copolymer composition, solution pH and by the addition of the water‐soluble poly(DMAA) segment. ¹H NMR analysis determined that, in water, the VBK units of the poly(DMAEMA‐ran‐VBK) random copolymer were segregated to the interior of the copolymer aggregate regardless of solution temperature and that poly(DMAEMA‐ran‐VBK)‐b‐poly(DMAA) block copolymers formed micelles above the LCST. In addition, the final random copolymer and block copolymer exhibited temperature dependent fluorescence due to the VBK units. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

The engineering and immobilization of penicillin G acylase onto thermo‐sensitive tri‐block copolymer system

In this work, the relationships between catalytic performances of penicillin G acylase (PGA) and the molar ratio of carrier, thermo‐sensitive tri‐block polymer, poly (N,N‐diethylacrylamide‐b‐ β‐hydroxyethyl methacrylate‐b‐glycidyl methacrylate) (PDEA‐b‐PHEMA‐b‐PGMA) were studied firstly, and result documented the optimal molar ratio was n_DEA:n_HEMA:n_GMA = 100:47:24, which presented a suitable lower critical solution temperature (LCST) of 35°C and the activity retention ratio of 80.62% (±0.50%). Based on the suitable carrier, immobilization conditions were investigated and optimized. When pH of solution, concentration of PGA, immobilized time, and immobilization temperature were 8.0, 1/10 (m/v), 16 hours, and 36°C, respectively, enzyme loading capacity (L), enzyme activity (Ea), and activity retention ratio (Ar) of PGA arrived at the highest value of 21 223 U, 16 199 U/g, and 93.50% (±0.50%), respectively. Besides, the response rate (Rr) of immobilized PGA was the same as free PGA, the reusable stability (Rs) was 77.00% (±1.00%) after using for 11 times, which indicated that the carrier has better compatibility with L, Ar, Rs, and Rr.     

Synthesis,pH‐ and temperature‐induced micellization and gelation of doubly hydrophilic triblock copolymer of poly(N,N‐dimethylamino‐2‐ethylmethacrylate)‐b‐poly(ethylene glycol)‐b‐poly(N,N‐dimethylamino‐2‐ethylmethacrylate) in aqueous solutions

A doubly hydrophilic triblock copolymer of poly(N,N‐dimethylamino‐2‐ethyl methacrylate)‐b‐Poly(ethylene glycol)‐b‐poly(N,N‐dimethylamino‐2‐ethylmethacrylate) (PDMAEMA‐b‐PEG‐b‐PDMAEMA) with well‐defined structure and narrow molecular weight distribution (M_w/M_n = 1.21) was synthesized in aqueous medium via atom transfer radical polymerization (ATRP) of N,N‐dimethylamino‐2‐ethylmethacrylate (DMAEMA) initiated by the PEG macroinitiator. The macroinitiator and triblock copolymer were characterized with ¹H NMR and gel permeation chromatography (GPC). Fluorescence spectroscopy, dynamic light scattering (DSL), transmittance measurement, and rheological characterization were applied to investigate pH‐ and temperature‐induced micellization in the dilute solution of 1 mg/mL when pH > 13 and gelation in the concentrated solution of 25 wt % at pH = 14 and temperatures beyond 80 °C. The unimer of R_h = 3.7 ± 0.8 nm coexisted with micelle of R_h = 45.6 ± 6.5 nm at pH 14. Phase separation occurred in dilute aqueous solution of the triblock copolymer of 1 mg/mL at about 50 °C. Large aggregates with R_h = 300–450 nm were formed after phase separation, which became even larger as R_h = 750–1000 nm with increasing temperature. The gelation temperature determined by rheology measurement was about 80 °C at pH 14 for the 25 wt % aqueous solution of the triblock copolymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5869–5878, 2008     

Copper catalyzed atom transfer radical copolymerization of glycidyl methacrylate and 2‐ethylhexyl acrylate

This investigation reports the atom transfer radical copolymerization (ATRcP) of glycidyl methacrylate (GMA) and 2‐ethylhexyl acrylate (EHA). Poly(glycidyl methacrylate) (PGMA) has easily transformable pendant oxirane group and poly(2‐ethylhexyl acrylate) (PEHA) has very low T_g. They are the important components of coating and adhesive materials. Copolymerization of GMA and EHA was carried out in bulk and in toluene at 70 °C at different molar feed ratios using CuCl as catalyst in combination with 2,2′‐bypyridine (bpy) as well as N,N,N′,N″,N″‐pentamethyl diethylenetriamine (PMDETA) as ligand. The molecular weight (M_n) and the polydispersity index (PDI) of the polymers were determined by GPC analysis. The molar composition of the copolymers was determined by ¹H NMR analysis. The reactivity ratios of GMA (r₁) and EHA (r₂) were determined using Finemann‐Ross and Kelen‐Tudos linearization methods and those had been compared with the literature values for conventional free radical copolymerization. The thermal properties of the copolymers were studied by DSC and TGA analysis. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6526–6533, 2009     

Radical polymerization of new functional monomer: Methacryloyl isocyanate containing 4‐chloro‐1‐phenol

New functional monomer methacryloyl isocyanate containing 4‐chloro‐1‐phenol (CPHMAI) was prepared on reaction of methacryloyl isocyanate (MAI) with 4‐chloro‐1‐phenol (CPH) at low temperature and was characterized with IR, ¹H, and ¹³C‐NMR spectra. Radical polymerization of CPHMAI was studied in terms of the rate of polymerization, solvent effect, copolymerization, and thermal properties. The rate of polymerization of CPHMAI has been found to be smaller than that of styrene under the same conditions. Polar solvents such as dimethylsulfoxide (DMSO) and N,N‐dimethyl formamide (DMF) were found to slow the polymerization. Copolymerization of CPHMAI (M₁) with styrene (M₂) in tetrahydrofuran (THF) was studied at 60°C. The monomer reactivity ratio was calculated to be r₁ = 0.49 and r₂ = 0.66 according to the method of Fineman—Ross. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 469–473, 2000     

Nitroxide‐mediated controlled statistical copolymerizations of N‐isopropylacrylamide with N‐tert‐butylacrylamide

The copolymerization of N‐isopropylacrylamide (NIPAM) and N‐tert‐butylacrylamide (TBAM) via conventional radical polymerization and nitroxide‐mediated polymerization (NMP) with N‐tert‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)]nitroxide (SG1) was investigated. The monomer reactivity ratios were determined to be 0.58 and 1.00 for NIPAM and TBAM, respectively. The reactivities were approximately the same at 120 and 60 °C in N,N‐dimethylformamide (DMF) and toluene, respectively, for the conventional copolymerizations and in DMF at 120 °C for NMP. Controlled/living characteristics for NMP were achieved with a 2,2′‐azobisisobutyronitrile/SG1 bimolecular system and a unimolecular polystyrene [poly(STY)]–SG1 macroinitiator in the presence of excess free SG1. Block copolymers of poly(N‐isopropylacrylamide‐stat‐N‐tert‐butylacrylamide) [poly(NIPAM‐stat‐TBAM)] with styrene {poly(N‐isopropylacrylamide‐stat‐N‐tert‐butylacrylamide)‐block‐polystyrene [poly(NIPAM‐stat‐TBAM)‐block‐poly(STY)]} were obtained by chain extension of either poly(NIPAM‐stat‐TBAM)–SG1 with styrene or poly(STY)–SG1 with NIPAM/TBAM. A comparison of the number‐average molecular weight calculated from the end‐group content with the number‐average molecular weight measured by gel permeation chromatography for poly(NIPAM‐stat‐TBAM)‐block‐poly(STY)–SG1 indicated that nearly all poly(NIPAM‐stat‐TBAM) chains were capped by SG1 and were thus living. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6410–6418, 2006     

H‐transfer reaction during decomposition of N‐(2‐methylpropyl)‐ N‐(1‐diethylphosphono‐2,2‐dimethylpropyl)‐N‐oxyl (SG1)‐based alkoxyamines

Thermal decomposition of four tertiary N‐(2‐methylpropyl)‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl)‐N‐oxyl (SG1)‐based alkoxyamines (SG1‐C(Me)₂‐C(O)‐OR, R = Me, tBu, Et, H) has been studied at different experimental conditions using ¹H and ³¹P NMR spectroscopies. This experiment represents the initiating step of methyl methacrylate polymerization. It has been shown that H‐transfer reaction occurs during the decomposition of three alkoxyamines in highly degassed solution, whereas no products of H‐transfer are detected during decomposition of SG1‐MAMA alkoxyamine. The value of the rate constant of H‐transfer for alkoxyamines 1 (SG1‐C(Me)₂‐C(O)‐OMe) and 2 ( SG1‐C(Me)₂‐C(O)‐OtBu) has been estimated as 1.7 × 10³ M^?1s^?1. The high influence of oxygen on decomposition mechanism is found. In particular, in poorly degassed solutions, nearly quantitative formation of oxidation product has been observed, whereas at residual pressure of 10^?5 mbar, the main products originate from H‐atom transfer reaction. The acidity of the reaction medium affects the decomposition mechanism suppressing the H‐atom transfer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis and characterization of amphiphilic poly(N‐vinyl pyrrolidone)‐b‐poly(ε‐caprolactone) copolymers by a combination of cobalt‐mediated radical polymerization and ring‐opening polymerization

An amphiphilic block copolymer of poly(N‐vinyl pyrrolidone)‐b‐poly(ε‐caprolactone) (PVP‐b‐PCL) was synthesized by a combination of cobalt‐mediated radical polymerization (CMRP) and ring‐opening polymerization (ROP). The micellar characteristics of this copolymer were subsequently investigated. PVP (M_n = 11,400, M_w/M_n = 1.32) was synthesized at 20 °C via CMRP using a molar ratio of [VP]₀/[V‐70]₀/[Co]₀ = 150/8/1. The PVP was then reacted with 2,2′‐azobis[2‐methyl‐N‐(2‐hydroxyethyl)propionamide] (VA‐086) to modify its cobalt complex chain end to a hydroxyl group. The cobalt (Co) content in the resulting PVP‐OH was 1.2 ppm, indicating that all of the covalent Co? C bonds were cleaved and reacted with VA‐086, and that the separated cobalt complexes were successfully removed. The ROP of CL was subsequently carried out using the produced PVP‐OH as a macroinitiator at 110 °C. The GPC trace of PVP‐b‐PCL was monomodal without any tailing caused by the residual PVP‐OH, indicating that the initiation efficiency was very high. The critical micelle concentration (CMC) of PVP‐b‐PCL (M_n = 18,000, M_w/M_n = 1.35) was 0.015 mg/mL. The PVP‐b‐PCL micelles were spherical in shape with an average diameter of 105 nm. The nanosized PVP‐b‐PCL micelles show promise as novel drug carriers in biomedical and pharmaceutical applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3078–3085, 2009     

Novel thermoresponsive fluorinated double‐hydrophilic poly{[N‐(2,2‐difluoroethyl)acrylamide]‐b‐[N‐(2‐fluoroethyl)acrylamide]} block copolymers

Novel thermoresponsive double‐hydrophilic fluorinated block copolymers were successfully synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization. Poly[N‐(2,2‐difluoroethyl)acrylamide] (P2F) was synthesized via RAFT polymerization of N‐(2,2‐difluoroethyl)acrylamide (M2F) using 2‐dodecylsulfanylthiocarbonylsulfanyl‐2‐methylpropionic acid (DMP) as the chain transfer agent (CTA) and 2,2′‐azobisisobutyronitrile (AIBN) as the initiator. The resulting P2F macroCTA was further chain extended with N‐(2‐fluoroethyl)acrylamide (M1F) to yield poly{[N‐(2,2‐difluoroethyl)acrylamide]‐b‐[N‐(2‐fluoroethyl)acrylamide]} (P2F‐b‐P1F) block copolymers with different lengths of the P1F block. Molecular weight and molecular weight distribution were determined by gel permeation chromatography. The average molecular weight (M_n) of the resulting polymers ranged from 2.9 × 10⁴ to 5.8 × 10⁴ depending on the length of the P1F block. The molecular weight distribution was low (M_w/M_n = 1.11–1.19). Turbidimetry by UV‐Visble (UV‐Vis) spectroscopy, dynamic light scattering, and in situ temperature‐dependent ¹H NMR measurements demonstrated that the P2F block underwent a thermal transition from hydrophilic to hydrophobic, which in turn induced self‐assembly from unimers to aggregates. Transmission electron microscopy studies demonstrated that polymeric aggregates formed from an aqueous solution of P2F‐b‐P1F at 60 °C were disrupted by cooling down to 20 °C and regenerated by heating to 60 °C. Temperature‐triggered release of a model hydrophobic drug, coumarin 102, was also demonstrated. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis of sugar‐based macromolecules via sono‐ATRP in miniemulsion

Ultrasound‐mediated atom transfer radical polymerization (sono‐ATRP) in miniemulsion media is used for the first time for the preparation of complex macromolecular architectures by a facile two‐step synthetic route. Initially, esterification reaction of sucrose or lactulose with α‐bromoisobutyryl bromide (BriBBr) is conducted to receive multifunctional ATRP macroinitiators with 8 initiation sites, followed by polymerization of n‐butyl acrylate (BA) forming arms of the star‐like polymers. The brominated lactulose‐based molecule was examined as an ATRP initiator by determining the activation rate constant (k_a) of the catalytic process in the presence of a copper(II) bromide/tris(2‐pyridylmethyl)amine (Cu^IIBr₂/TPMA) catalyst in both organic solvent and for the first time in miniemulsion media, resulting in k_a = (1.03 ± 0.01) × 10⁴ M^?1 s^?1 and k_a = (1.16 ± 0.56) × 10³ M^?1 s^?1, respectively. Star‐like macromolecules with a sucrose or lactulose core and poly(n‐butyl acrylate) (PBA) arms were successfully received using different catalyst concentration. Linear kinetics and a well‐defined structure of synthesized polymers reflected by narrow molecular weight distribution (M_w/M_n = 1.46) indicated 105 ppm wt of catalyst loading as concentration to maintain controlled manner of polymerization process. ¹H NMR analysis confirms the formation of new sugar‐inspired star‐shaped polymers.     

Functional syndiotactic poly(β‐hydroxyalkanoate)s via stereoselective ring‐opening copolymerization of rac‐β‐butyrolactone and rac‐allyl‐β‐butyrolactone

The copolymerization of racemic β‐butyrolactone (rac‐BL^Me) with racemic “allyl‐β‐butyrolactone” (rac‐BL^allyl) in toluene, catalyzed by the discrete amino‐alkoxy‐bis(phenolate) yttrium‐amido complex 1 , gave new poly(β‐hydroxyalkanoate)s with unsaturated side chains. The poly(BL^Me‐co‐BL^allyl) copolymers produced have a highly syndiotactic backbone structure (P_r = 0.80–0.84) with a random enchainment of monomer units, as evidenced by ¹³C NMR, and high molecular weight (M_n up to 58,000 g mol^?1) with a narrow polydispersity (M_w/M_n = 1.07–1.37), as determined by GPC. The comonomer incorporation (5–50 mol % rac‐BL^allyl) was a linear function of the feed ratio. The pendant vinyl bond of the side‐chains in those poly(BL^Me‐co‐BL^allyl) copolymers allowed the effective introduction of hydroxy or epoxy groups via dihydroxylation, hydroboration‐oxidation or epoxidation reactions. NMR studies indicated that all of these transformations proceed in an essentially quantitative conversion and do not affect the macromolecular architecture. Some thermal properties (T_m, ΔH_m, T_g) of the prepared polymers have been also evaluated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3177–3189, 2009