Synthesis of functional graft copolymers by solution copolymerization and their evaluation as dispersants in nonaqueous phase dispersion polymerization

The poly(HEMA‐co‐MMA‐g‐PMMA) graft copolymer was prepared with a poly(methyl methacrylate) (PMMA) macromonomer, 2‐hydroxyethyl methacrylate (HEMA), and methyl methacrylate (MMA), and its application as a dispersant for the nonaqueous phase dispersion polymerization of polystyrene (PST) was investigated. Monodisperse PST particles were obtained with two‐dimensionally tailored graft copolymers, with the number of grafted chains controlled and the polar component (HEMA) in the backbone chains balanced. As for the reactor, a stirred vessel with moderate agitation yielded uniform polymer particles, whereas sealed glass ampules with an overturning motion yielded broader size distributions. Increasing the polarity of the solvent in the continuous phase yielded smaller polymer particles with a gradual deterioration of monodispersity. Uniform polymer particles with a coefficient of variation of less than 6% were obtained up to 30 wt % solid contents. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1788–1798, 2003     

Synthesis of poly(2‐hydroxyethyl methacrylate) in protic media through atom transfer radical polymerization using activators generated by electron transfer

Atom transfer radical polymerization (ATRP) using activators generated by electron transfer (AGET) was investigated for the controlled polymerization of 2‐hydroxyethyl methacrylate (HEMA) in a protic solvent, a 3/2 (v/v) mixture of methyl ethyl ketone and methanol. The AGET process enabled ATRP to be started with an air‐stable Cu(II) complex that was reduced in situ by tin(II) 2‐ethylhexanoate. The reaction temperature, Cu catalysts with different ligands, and variation of the initial concentration ratio of HEMA to the initiator were examined for the synthesis of well‐controlled poly(2‐hydroxyethyl methacrylate) and a poly(methyl methacrylate)‐b‐poly(2‐hydroxyethyl methacrylate) block copolymer. The level of control in AGET ATRP was similar to that in normal ATRP in protic solvents, and this resulted in a linear increase in the molecular weight with the conversion and a narrow molecular weight distribution (weight‐average molecular weight/number‐average molecular weight < 1.3). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3787–3796, 2006     

Precipitation polymerization of 2‐hydroxyethyl methacrylate in supercritical carbon dioxide

We report the successful precipitation polymerization of 2‐hydroxyethyl methacrylate (HEMA) in supercritical carbon dioxide (scCO₂) at pressures ranging from 15 to 27 MPa utilizing 2, 2′‐azobisisobutyronitrile (AIBN) as a free radical initiator. The effects of the reaction pressure, initiator concentration, monomer concentration, reaction temperature, and reaction time were investigated. Analyses by scanning electron microscopy (SEM) indicated that in all reaction conditions, polymerization in the absence of stabilizer led to the formation of large aggregates of partially coalesced particles, with diameters of approximate 1–10 µm. Analyses by gel permeation chromatography (GPC) indicated that for the reaction pressure, initiator concentration, monomer concentration, reaction temperature, and reaction time studied there are appreciable effect on product molecular weight. Copyright © 2011 John Wiley & Sons, Ltd.     

Magnetic poly(2‐hydroxyethyl methacrylate‐co‐ethylene dimethacrylate) microspheres by dispersion polymerization

Crosslinked poly(2‐hydroxyethyl methacrylate)‐based magnetic microspheres were prepared in a simple one‐step procedure by dispersion polymerization in the presence of several kinds of iron oxides. Cellulose acetate butyrate and dibenzoyl peroxide were used as steric stabilizer and polymerization initiator, respectively, and ethylene dimethacrylate was a crosslinking agent. The resulting product was characterized in terms of particle size, particle size distribution, iron(III) content, and magnetic properties. In the presence of needle‐like maghemite in the polymerization mixture and under suitable conditions, magnetic microspheres with relatively narrow size distribution were formed. An increase in the particle size and, at the same time, a decrease in molecular weight of uncrosslinked polymers resulted, as the continuous phase became richer in 2‐methylpropan‐1‐ol. Coercive force of needle‐like maghemite‐containing particles was higher than that of cubic magnetite‐loaded microspheres. Coercive force increased with the decreasing iron content in the particles. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1161–1171, 2000     

Synthesis and characterization of well‐defined poly(2‐hydroxyethyl methacrylate‐co‐styrene)‐graft‐poly(ε‐caprolactone) by sequential controlled polymerization

A new graft copolymer, poly(2‐hydroxyethyl methacrylate‐co‐styrene) ‐graft‐poly(?‐caprolactone), was prepared by combination of reversible addition‐fragmentation chain transfer polymerization (RAFT) with coordination‐insertion ring‐opening polymerization (ROP). The copolymerization of styrene (St) and 2‐hydroxyethyl methacrylate (HEMA) was carried out at 60 °C in the presence of 2‐phenylprop‐2‐yl dithiobenzoate (PPDTB) using AIBN as initiator. The molecular weight of poly (2‐hydroxyethyl methacrylate‐co‐styrene) [poly(HEMA‐co‐St)] increased with the monomer conversion, and the molecular weight distribution was in the range of 1.09 ～ 1.39. The ring‐opening polymerization (ROP) of ?‐caprolactone was then initiated by the hydroxyl groups of the poly(HEMA‐co‐St) precursors in the presence of stannous octoate (Sn(Oct)₂). GPC and ¹H‐NMR data demonstrated the polymerization courses are under control, and nearly all hydroxyl groups took part in the initiation. The efficiency of grafting was very high. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5523–5529, 2004     

Solid‐supported synthesis of well‐defined amphiphilic block copolymer from methacrylates

A new facile method for preparation of an amphiphilic block copolymer via a one‐pot sequential atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and 2‐hydroxyethyl methacrylate (HEMA) on solid support was developed. As a model homopolymerization for the solid‐supported block copolymerization, ATRPs of MMA and HEMA in toluene and in 2‐butanone/1‐propanol solvent system were carried out, respectively. Crosslinked polystyrene beads bearing 2‐bromoisobutyrate moieties successfully initiated the polymerizations of MMA and HEMA in controlled manner. On the basis of the successful results, the one‐pot synthesis of amphiphilic block copolymer by changing the reaction medium was performed. After the ATRP of MMA in toluene at 90 °C for 1 h, the poly(MMA) formed on the beads were washed by continuous flow of 2‐butanone/1‐propanol under nitrogen with the aid of a glass filter in a U‐shaped glass vessel. Then, 2‐butanone/1‐propanol, copper chloride (I), 2,2′‐bipyridyl, and HEMA were added and heated at 50 °C for 48 h with shaking the vessel, followed by treatment with trifluoroacetic acid to isolate the well‐defined amphiphilic block copolymer, poly(MMA‐b‐HEMA). These demonstrated the feasibility of the present strategy for well‐defined synthesis of amphiphilic block copolymers via a one‐pot procedure. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1990–1997, 2008     

Mono- or narrow disperse poly(methacrylate-co-divinylbenzene) microspheres by precipitation polymerization

Precipitation copolymerizations of five mono-vinyl methacrylic monomers including methyl methacrylate (MMA), butyl methacrylate (BMA), dodecyl methacrylate (DMA), glycidyl methacrylate (GMA), and hydroxyethyl methacrylate (HEMA) with divinylbenzene (DVB), in a wide range of comonomer composition, were carried out in acetonitrile to form mono- or narrow disperse crosslinked copolymer microspheres. In addition, two divinyl methacrylic monomers, ethylene glycol dimethacrylate (EGDMA) and triethylene glycol dimethacrylate (TEGDMA), were also copolymerized with DVB, and optionally a third comonomer (GMA or HEMA), to yield similar microspheres in acetonitrile. The possibility of creating porosity was explored for some of the copolymer particles. All these microspheres have clean surfaces due to the absence of any added steric or ionic stabilizer, and they are in the size of the micrometer range, varying from 1 to 7 µm, depending on the type and content of the methacrylic comonomer. Particle size distribution, surface morphology, internal texture, and porosity properties of these particles were studied by a Coulter Multisizer, a scanning electron microscope, a transmission electron microscope, and an Autosorb-1. The effects of comonomers on microsphere formation and morphology are described. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2899–2907, 1999     

Simultaneous reversible addition fragmentation chain transfer and ring‐opening polymerization

The simultaneous ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) and 2‐hydroxyethyl methacrylate (HEMA) polymerization via reversible addition fragmentation chain transfer (RAFT) chemistry and the possible access to graft copolymers with degradable and nondegradable segments is investigated. HEMA and ε‐CL are reacted in the presence of cyanoisopropyl dithiobenzoate (CPDB) and tin(II) 2‐ethylhexanoate (Sn(Oct)₂) under typical ROP conditions (T > 100 °C) using toluene as the solvent in order to lead to the graft copolymer PHEMA‐g‐PCL. Graft copolymer formation is evidenced by a combination of size‐exclusion chromatography (SEC) and NMR analyses as well as confirmed by the hydrolysis of the PCL segments of the copolymer. With targeted copolymers containing at least 10% weight of PHEMA and relatively small PHEMA backbones (ca. 5,000–10,000 g mol^?1) the copolymer grafting density is higher than 90%. The ratio of free HEMA‐PCL homopolymer produced during the “one‐step” process was found to depend on the HEMA concentration, as well as the half‐life time of the radical initiator used. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3058–3067, 2008     

Novel copolymer networks via the combination of polyaddition and anionic polymerization

A two‐step synthetic route to novel copolymer networks, consisting of polymethacrylate and polyacetal components, was developed by combining the polyaddition and anionic polymerization techniques. The functional polymethacrylates containing hydroxyl or vinyloxyl side groups were used as crosslinkers. They were anionically synthesized as follows: the copolymer of 2‐hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) was prepared by the anionic copolymerization of 2‐(trimethylsiloxy)ethyl methacrylate and MMA, followed by hydrolysis. The copolymer poly(HEMA‐co‐MMA) thus obtained possessed a hydroxyl group in each of its HEMA units. Another kind of vinyloxyl‐containing (co)polymer was prepared by the anionic homopolymerization of 2‐(vinyloxy)ethyl methacrylate (VEMA) or its copolymerization with MMA. The resulting (co)polymer possessed reactive vinyloxyl side groups. The copolymer networks were obtained by reacting each of the above‐mentioned (co)polymers with a polyacetal prepared via the polyaddition between a divinyl ether and a diol. Three divinyl ethers (ethylene glycol divinyl ether, 1,4‐butanediol divinyl ether, and 1,6‐hexanediol divinyl ether) and three diols (ethylene glycol, 1,4‐butanediol, and 1,6‐hexanediol) were employed as monomers in the polyaddition step, and their combinations generated nine kinds of polyacetals. When a polyaddition reaction was terminated with a divinyl ether monomer, a polyacetal with two vinyloxyl end groups was obtained, which could further react with the hydroxyl groups of poly(HEMA‐co‐MMA) to generate a copolymer network. On the other hand, when a diol was used as terminator in the polyaddition, the resulting polyacetal possessed two hydroxyl end groups, which could react with the vinyloxyl groups of poly(VEMA) or poly(VEMA‐co‐MMA), to generate a copolymer network. All the copolymer networks exhibited degradation in the presence of acids. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 117–126, 2001     

Role of dispersion stabilizer with hydroxy groups in preparation of monodisperse polylactide microspheres

Monodisperse poly(D ,L ‐lactide) (PDLLA) microspheres were prepared by dispersion polymerization of D ,L ‐lactide in xylene/heptane (1/2, v/v) with poly[(dodecyl methacrylate)‐co‐(2‐hydroxyethyl methacrylate)] (P(DMA‐co‐HEMA)) as a dispersion stabilizer. P(DMA‐co‐HEMA) contains hydroxy groups, which act as an initiation group for pseudoanionic dispersion polymerization. The best coefficient of variation (CV) values concerning particle diameter distribution and the particle diameter of obtained PDLLA microspheres were 3.7% and 5.3 μm, respectively. The particle diameter decreased with increasing concentration of P(DMA‐co‐HEMA) and HEMA maintained low CV (<10%) values. As a result, monodisperse PDLLA microspheres ranging from 1.3 to 5.3 μm were obtained. In addition, it was found that monodisperse PDLLA microspheres were obtained by sufficient capture of growing polymers and monomers in the particle growth stage. Therefore, the HEMA concentration in P(DMA‐co‐HEMA) strongly affecting the capturing capability is the most important factor. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5230–5240, 2009     

Effect of the reaction parameters on the particle size in the dispersion polymerization of 2‐hydroxyethyl and glycidyl methacrylate in the presence of a ferrofluid

The precipitation of Fe₃O₄ from an aqueous solution with ammonium hydroxide produced nanoparticles that were coated with a layer of oleic acid [or, in some cases, poly(ethylene oxide) or poly(vinylpyrrolidone)] before their dispersion into the organic phase. The encapsulation of magnetite nanoparticles in poly(2‐hydroxyethyl methacrylate) or poly(2‐hydroxyethyl methacrylate‐co‐glycidyl methacrylate) microparticles was achieved by dispersion polymerization in toluene/2‐methylpropan‐1‐ol. Magnetic poly(glycidyl methacrylate) microparticles were obtained in the presence of poly(ethylene oxide) at the magnetite/monomer interface. The particles containing up to 20 wt % iron maintained their discrete nature and did not aggregate. The effect of the reaction medium polarity, the concentrations of the monomer, initiator, and stabilizer, and the temperature on the particle size, particle size distribution, and iron and oxirane group contents was studied. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1848–1863, 2003     

Samarium enolate on crosslinked polystyrene beads. III. Anionic initiator for well‐defined synthesis of poly(hydroxyethyl methacrylate) on solid support

A solid‐supported samarium enolate successfully initiated the polymerization of 2‐(trimethylsilyloxy)ethyl methacrylate (TMS‐HEMA) through the living anionic process. In addition, the silyl group was readily removed by treatment of the beads with a weak acid to afford the corresponding well‐defined poly(methacrylate) having a hydroxyethyl group in the side chain (PHEMA). The hydroxyl group of the immobilized PHEMA on the beads was successfully acetylated to give poly(2‐acetoxyethyl methacrylate), which could be quantitatively isolated from the beads by trifluoroacetic acid treatment. Moreover, the hydroxyl group of the immobilized PHEMA could be utilized as an initiator for acid promoted ring opening polymerization of lactone to yield the corresponding graft copolymer. In this method, the residual and excess reagents could be removed by filtration, which demonstrated the applicability of the present technique to a novel method for construction of functional polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4417–4423, 2004     

Poly(2‐hydroxyethyl methacrylate‐co‐N,O‐dimethacryloylhydroxylamine) particles by dispersion polymerization

Poly(2‐hydroxyethyl methacrylate‐co‐N,O‐dimethacryloylhydroxylamine) particles were prepared by dispersion polymerization in toluene/2‐methylpropan‐1‐ol medium using cellulose acetate butyrate and dibenzoyl peroxide (BPO) as a steric stabilizer and initiator, respectively. The particle size was reduced with decreasing solvency of the reaction medium (more nuclei were generated) because the critical chain length of the precipitated oligomers decreased with an increasing toluene content, which is a poorer solvent for the polymer than 2‐methylpropan‐1‐ol. There is an optimum initiator concentration (2 wt % BPO relative to monomers) for producing low‐polydispersity particles under given conditions. Additionally, discrete spherical particles were obtained at a low monomer concentration and/or higher polymerization temperature. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1625–1632, 2002     

Viscosity,particle size distribution,and structural investigation of tetramethyloxysilane/2‐hydroxyethyl methacrylate sols during the sol–gel process with acid and base catalysts

The tetramethoxysilane (TMOS)/2‐hydroxylethyl methacrylate (HEMA) hybrid gels were synthesized with acid and base catalysts, via the in situ polymerization of HEMA, with and without the cosolvent methanol. With methanol in the TMOS/HEMA sol, the enhanced esterification and depolymerization reactions of the silanols resulted in a slower growth of silica particles. The silica particles that were synthesized with an acid catalyst were less than 40 nm. The thermal resistance of the poly(2‐hydroxyethyl methacrylate) (PHEMA) chains was enhanced by the addition of colloidal silica. The Fourier transform infrared characterizations and the exothermal peaks on the differential scanning calorimetry traces of these hybrid gels indicated chemical hybridization occurring as a result of condensation of the colloid silica and PHEMA at higher temperatures. Hence, the residual weight content of the hybrid gel after its synthesis with the base catalyst was even higher than the content of TMOS in the hybrid sol. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3476–3486, 2004     

Synthesis of high‐molecular‐weight linear methacrylate copolymers with spiropyran side groups: Conformational changes of single molecules in solution and on surfaces

P(BMA‐co‐HEMA‐spiropyran) was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization of butyl methacrylate (BMA) and 2‐(trimethylsilyloxy)‐ethyl methacrylate (HEMA‐TMS), removal of the TMS‐protective groups, and the polymer analogous esterification of the hydroxyethyl side chains with a spiropyran containing a carboxylic acid group. UV‐induced conformational changes of the synthesized macromolecules and low‐molecular‐weight spiropyran molecules were studied. Rate constants and half‐life times of the ring closure reaction from zwitterionic merocyanine to the spiropyran species were determined in the presence and absence of mica‐dispersed particles in toluene both with the free spiropyran and the polymer‐bound spiropyran. Scanning force microscopy was used to visualize the conformation of spiropyran‐decorated single macromolecular chains and agglomerated polymer‐bound merocyanine adsorbed on mica. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1274–1283, 2009     

Synthesis and characterization of amphiphilic copolymer of linear poly(ethylene oxide) linked with [poly(styrene‐co‐2‐hydroxyethyl methacrylate)‐graft‐poly(ε‐caprolactone)] using sequential controlled polymerization

A well‐defined amphiphilic copolymer of ‐poly(ethylene oxide) (PEO) linked with comb‐shaped [poly(styrene‐co‐2‐hydeoxyethyl methacrylate)‐graft‐poly(ε‐caprolactone)] (PEO‐b‐P(St‐co‐HEMA)‐g‐PCL) was successfully synthesized by combination of reversible addition‐fragmentation chain transfer polymerization (RAFT) with ring‐opening anionic polymerization and coordination–insertion ring‐opening polymerization (ROP). The α‐methoxy poly(ethylene oxide) (mPEO) with ω,3‐benzylsulfanylthiocarbonylsufanylpropionic acid (BSPA) end group (mPEO‐BSPA) was prepared by the reaction of mPEO with 3‐benzylsulfanylthiocarbonylsufanyl propionic acid chloride (BSPAC), and the reaction efficiency was close to 100%; then the mPEO‐BSPA was used as a macro‐RAFT agent for the copolymerization of styrene (St) and 2‐hydroxyethyl methacrylate (HEMA) using 2,2‐azobisisobutyronitrile as initiator. The molecular weight of copolymer PEO‐b‐P(St‐co‐HEMA) increased with the monomer conversion, but the molecular weight distribution was a little wide. The influence of molecular weight of macro‐RAFT agent on the polymerization procedure was discussed. The ROP of ε‐caprolactone was then completed by initiation of hydroxyl groups of the PEO‐b‐P(St‐co‐HEMA) precursors in the presence of stannous octoate (Sn(Oct)₂). Thus, the amphiphilic copolymer of linear PEO linked with comb‐like P(St‐co‐HEMA)‐g‐PCL was obtained. The final and intermediate products were characterized in detail by NMR, GPC, and UV. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 467–476, 2006     

Water transport in 2‐hydroxyethyl methacrylate copolymer irradiated by γ rays in air and related phenomena

The water transport in 2‐hydroxyethyl methacrylate copolymer (HEMA copolymer) irradiated by γ rays in air is investigated. The sorption data of deionized water transport in HEMA copolymer subjected to various dosages of γ‐ray irradiation are in excellent agreement with the theoretical model that accounts for case I, case II, and anomalous transport. The diffusion coefficient for case I and the velocity for case II satisfy the Arrhenius equation for all dosage levels. The transport process is exothermic and the equilibrium–swelling ratio satisfies the van't Hoff plot. The studies of the glass transition temperature of the irradiated HEMA copolymer, the pH value of deionized water after irradiation treatment, and the quantitative determination of water structures in the HEMA copolymer hydrogel are helpful in analyzing the irradiation effect on water transport in the HEMA copolymer. The effect of irradiation on the optical properties of the HEMA copolymer is also analyzed. The transmittance of a standard specimen with saturated water is lower than that before the water treatment because of the creation of holes. However, because of the formation of color centers, the color of the copolymer becomes yellow to brown and the UV cutoff wavelength of the HEMA copolymer shifts to the longer wavelength side with increasing irradiation dosage. Some of the color centers can be annihilated after water treatment. The buckled pattern on the outer surface is observed when the HEMA copolymer irradiated by a γ ray in air is immersed in the water. This phenomenon is explained by the inhomogeneous distribution of crosslinking density. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 659–671, 2000     

Synthesis of a novel copolymer using glycogen and poly(lactide) as a carrier of dual drugs—ornidazole and ofloxacin

Biodegradability and biocompatibility are two crucial prerequisites for a promising therapeutic vehicle. Herein, a novel biocompatible copolymer has been synthesized using glycogen and polylactide (PLA). Glycogen, a naturally occurring biopolymer has been functionalized by methacrylation. On the other hand, lactide has been polymerized through ring opening polymerization (ROP), initiated by hydroxyethyl methacrylate (HEMA) and catalyzed by tin (II) 2‐ethyl hexanoate. Finally, the synthesized two substrates (i.e., glycogen methacrylate and PLA‐HEMA) are covalently connected by free‐radical polymerization, initiated by AIBN. The structure of the developed copolymer has been confirmed using ¹H and ¹³C NMR spectral analyses. The gel characteristics have been evaluated by rheological studies, while the morphological assessment has been investigated by FESEM analysis. In vitro cytocompatibility study reveals that the hydrogel (Gly‐co‐PLA) is biocompatible. The in vitro and in vivo release studies demonstrate the excellent pH‐sensitive control release profile of dual drugs: ornidazole and ofloxacin. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1697–1703     

Water sorption by poly(tetrahydrofurfuryl methacrylate‐co‐2‐hydroxyethyl methacrylate). I. A mass‐uptake study

Cylindrical samples (≈5 mm × 20 mm) of poly(2‐hydroxyethyl methacrylate) and copolymers of 2‐hydroxyethyl methacrylate and furfuryl methacrylate were prepared, and the sorption of water into these cylinders was studied by the mass‐uptake method and by the measurement of the volume change at equilibrium. The equilibrium water content and volume change for the cylinders both varied systematically with the copolymer composition. The diffusion of water into the cylinders followed Fickian behavior, with the diffusion coefficients, dependent on the copolymer composition, varying from 2.00 × 10⁻¹¹ m²s⁻¹ for poly(2‐hydroxyethyl methacrylate) to 5.00 × 10⁻¹² m²s⁻¹ for poly(2‐hydroxyethyl methacrylate‐co‐tetrahydrofurfuryl methacrylate) with a 1 : 4 composition. The polymers that were rich in 2‐hydroxyethyl methacrylate were characterized by a water‐sorption overshoot, which was attributed to a slow reorientation of the polymer chains in the swollen rubbery regions formed after water sorption. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1939–1946, 2000     

PLA‐based nanoparticles with tunable hydrophobicity and degradation kinetics

In this work, the preparation of poly(lactic acid) (PLA)‐based degradable nanoparticles (NPs) with tunable hydrophobicity and degradation kinetics via starved emulsion free‐radical polymerization is studied. The synthesis of macromonomers, constituted of a tunable number of lactic acid units functionalized with 2‐hydroxyethyl methacrylate (HEMA), has been performed via bulk ring opening polymerization (ROP) of L, L‐ lactide catalyzed with 2‐ethylhexanoic acid tin (II) salt. Macromonomers were characterized through SEC, NMR, and FTIR and are subsequently polymerized through monomer‐starved semi‐batch emulsion polymerization (MSSEP). The effect on the polymerization process of various emulsifiers on the final diameter and particle size distribution has been studied. The resulting PLA‐based NPs are characterized by a narrow size distribution and a small particle size, down to 25 nm. Finally, a degradation study of selected NPs has been carried out to verify their degradability in aqueous media. It has been demonstrated the complete degradability of these PLA‐based NPs which occurs upon the hydrolysis of the PLA pendant chains leaving poly‐HEMA chains, which, being hydrophilic causes the NPs to dissolve in the aqueous suspension. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012