Thiocarbonylthio end group removal from RAFT‐synthesized polymers by a radical‐induced process

The removal of thiocarbonylthio end groups by radical‐addition‐fragmentation‐ coupling from polymers synthesized by RAFT polymerization has been studied. We found that a method, which involves heating the polymer with a large excess (20 molar equivalents) of azobis(isobutyronitrile) (AIBN), while successful with methacrylic polymers, is less effective with styrenic or acrylic polymers and provides only partial end group removal. This is attributed to the propagating radicals generated from the latter polymers being poor radical leaving groups relative to the cyanoisopropyl radical. Similar use of lauroyl peroxide (LPO) completely removes the thiocarbonylthio groups from styrenic or acrylic polymers but, even with LPO in large excess, produces a polymer with a bimodal molecular weight distribution. The formation of a peak of double molecular weight is indicative of the occurrence of self‐termination and ineffective radical trapping. We now report that by use of a combination of LPO (2 molar equivalents) and AIBN (20 molar equivalents) we are able to completely remove thiocarbonylthio end groups of styrenic or acrylic polymers and minimize the occurrence of self termination. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6704–6714, 2009     

Star polymers by cross‐linking of linear poly(benzyl‐L‐glutamate) macromonomers via free‐radical and RAFT polymerization. A simple route toward peptide‐stabilized nanoparticles

Poly(benzyl‐L ‐glutamate) (PBLG) macromonomers were synthesized by N‐carboxyanhydride (NCA) polymerization initiated with 4‐vinyl benzylamine. MALDI‐ToF analysis confirmed the presence of styrenic end‐groups in the PBLG. Free‐radical and RAFT polymerization of the macromonomer in the presence of divinyl benzene produced star polymers of various molecular weights, polydispersity, and yield depending on the reaction conditions applied. The highest molecular weight (M_w) of 10,170,000 g/mol was obtained in a free‐radical multibatch approach. It was shown that the PBLG star polymers can be deprotected to obtain poly(glutamic acid) star polymers, which form water soluble pH responsive nanoparticles. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Temperature and crosslinking effects on the swelling of poly(isoprene) in isopiestic conditions

Isopiestic measurements of solvent uptake have been made in the synthetic isoprene/benzene system for both crosslinked and uncrosslinked polymers in order to revisit the question of the swelling activity parameter S. Both the nonzero value of S at zero swelling and the appearance of a peak in S vs. degree of swelling have been observed in some solvent/rubber pairs and we here investigate both the crosslink and temperature dependencies of these phenomena. The data analysis is an extension of prior work from this laboratory using continuum thermodynamics concepts and avoiding molecular models in an attempt to establish the fundamental phenomenology of the process and the validity or lack of validity of the hypothesis that the mixing and elastic contributions to the free energy of networks are separable. We present results from measurements in benzene vapors at temperatures between 10 and 55°C for an uncrosslinked rubber and rubbers crosslinked with 1, 5, 10, and 15 parts per hundred dicumyl peroxide. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 817–826, 1997     

End group transformations of RAFT‐generated polymers with bismaleimides: Functional telechelics and modular block copolymers

End group activation of polymers prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization was accomplished by conversion of thiocarbonylthio end groups to thiols and subsequent reaction with excess of a bismaleimide. Poly(N‐isopropylacrylamide) (PNIPAM) was prepared by RAFT, and subsequent aminolysis led to sulfhydryl‐terminated polymers that reacted with an excess of 1,8‐bismaleimidodiethyleneglycol to yield maleimido‐terminated macromolecules. The maleimido end groups allowed near‐quantitative coupling with model low molecular weight thiols or dienes by Michael addition or Diels‐Alder reactions, respectively. Reaction of maleimide‐activated PNIPAM with another thiol‐terminated polymer proved an efficient means of preparing block copolymers by a modular coupling approach. Successful end group functionalization of the well‐defined polymers was confirmed by combination of UV–vis, FTIR, and NMR spectroscopy and gel permeation chromatography. The general strategy proved to be versatile for the preparation of functional telechelics and modular block copolymers from RAFT‐generated (co)polymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5093–5100, 2008     

Synthesis of well-defined polychlorostyrenes by living radical polymerization with 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl

Radical polymerization of 2-, 3-, and 4-chlorostyrenes (ClSts) was investigated with benzoyl peroxide (BPO) as an initiator, in the presence of 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO). The polymerization was performed in bulk for 3.5 h at 95°C and then continued for a defined time at 125°C to give the corresponding poly(ClSt)s with narrow polydispersity in high yield. It was found that the polymerization proceeded in accordance with a living mechanism in all cases, because the molecular weight of the resulting polymers was proportional to the conversion, and inversely proportional to the initial concentration of MTEMPO. Furthermore, the polymers obtained from 2- and 3-ClSts quantitatively act as initiators for the polymerization in the living radical manner, of styrene to give the corresponding block copolymers, except for poly(4-ClSt). The thermal stability of the living poly(ClSt)s was found to decrease in the order of 2- > 3- > 4-ClSt on the basis of the results of their postpolymerizations. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2371–2378, 1997     

Fluorocarbon‐ended polymers: Metal catalyzed radical and living radical polymerizations initiated by perfluoroalkylsulfonyl halides

Perfluoroalkylsulfonyl chlorides and bromides initiate metal catalyzed free radical polymerization of both hydrocarbon and fluorocarbon monomers affording polymers with perfluoroalkyl end groups. In the case of styrene (S) and methyl methacrylate (MMA) with Cu‐based catalysts the process affords polymers with a relatively narrow molecular weight distribution and linear dependence of molecular weight on conversion, suggesting that a living radical polymerization mechanism occurs. The orders of reaction in monomer, initiator and catalyst for these polymerizations were determined. In the case of PMMA, the detailed structure of a perfluorobutane chain‐end was determined by NMR analysis. Perfluoroalkylsulfonyl chlorides are stable in neutral aqueous media. This permits their use as initators for fluoroolefin polymerizations in H₂O. Poly(tetrafluoroethylene‐co‐hexafluoropropylene) was obtained in good yield with few ionic end groups. The aqueous fluoroolefin polymerization appears to be catalyzed by metal zero species from the reactor walls. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3313–3335, 2000     

Synthesis and characterization of mid‐ and end‐chain functional telechelics by controlled polymerization methods and coupling processes

Well‐defined polystyrene‐ (PSt) or poly(ε‐caprolactone) (PCL)‐based polymers containing mid‐ or end‐chain 2,5 or 3,5‐ dibromobenzene moieties were prepared by controlled polymerization methods, such as atom transfer radical polymerization (ATRP) or ring opening polymerization (ROP). 1,4‐Dibromo‐2‐(bromomethyl)benzene, 1,3‐dibromo‐5‐(bromomethyl)benzene, and 1,4‐dibromo‐2,5‐di(bromomethyl)benzene were used as initiators in ATRP of styrene (St) in conjunction with CuBr/2,2′‐bipyridine as catalyst. 2,5‐Dibromo‐1,4‐(dihydroxymethyl)benzene initiated the ROP of ε‐caprolactone (CL) in the presence of stannous octoate (Sn(Oct)₂) catalyst. The reaction of these polymers with amino‐ or aldehyde‐functionalized monoboronic acids, in Suzuki‐type couplings, afforded the corresponding telechelics. Further functionalization with oxidable groups such as 2‐pyrrolyl or 1‐naphthyl was attained by condensation reactions of the amino or aldehyde groups with low molecular weight aldehydes or amines, respectively, with the formation of azomethine linkages. Preliminary attempts for the synthesis of fully conjugated poly(Schiff base) with polymeric segments as substituents, by oxidative polymerization of the macromonomers, are presented. All the starting, intermediate, or final polymers were structurally analyzed by spectral methods (¹H NMR, ¹³C NMR, and IR). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 727–743, 2006     

A versatile approach for the preparation of end‐functional polymers and block copolymers by stable radical exchange reactions

A versatile strategy for the preparation of end‐functional polymers and block copolymers by radical exchange reactions is described. For this purpose, first polystyrene with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl end group (PS‐TEMPO) is prepared by nitroxide‐mediated radical polymerization (NMRP). In the subsequent step, these polymers are heated to 130 °C in the presence of independently prepared TEMPO derivatives bearing hydroxyl, azide and carboxylic acid functionalities, and polymers such as poly(ethylene glycol) (TEMPO‐PEG) and poly(ε‐caprolactone) (TEMPO‐PCL). Due to the simultaneous radical generation and reversible termination of the polymer radical, TEMPO moiety on polystyrene is replaced to form the corresponding end‐functional polymers and block copolymers. The intermediates and final polymers are characterized by ¹H NMR, UV, IR, and GPC measurements. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2387–2395     

Functionalization of carbon black nanoparticles with poly(vinylidene fluoride)

The surface of carbon black (CB) nanoparticles was functionalized with poly(vinylidene fluoride) (PVDF) either by trapping of macroradicals or by cycloaddition. PVDF with two iodine end groups (I‐PVDF‐I) obtained from iodine transfer polymerization in supercritical CO₂ was heated in the presence of CB and the C? I bond was cleaved resulting in a reaction between the macroradical and the CB surface. To allow for cycloaddition of PVDF to the CB surface for a number of polymers, the iodine end groups were replaced by azide end groups. In addition, microwave irradiation was applied to the functionalization. The influence of temperature, time, polymer concentration, and polymer molar mass on the functionalization reaction was examined. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

A novel synthesis of reactive polymers with pendant halomethyl groups by the polyaddition reaction of bis(epoxide)s with bis(chloroacetoxy)esters or bis(bromoacetoxy)esters

New reactive polymers with pendant halomethyl groups were successfully synthesized by polyaddition reactions of bis(epoxide)s with bis(chloroacetoxy)ester such as 1,4-bis [(chloroacetoxy)methyl]benzene (BCAMB) or 1,4-bis[(bromoacetoxy)methyl]benzene (BBAMB) using quaternary onium salts or crown ether complexes as catalysts. The polyaddition reaction of diglycidyl ether of bisphenol A (DGEBA) with BCAMB proceeded very smoothly with high yields (83–96%) by the addition of quaternary onium salts such as tetrabutylphosphonium bromide (TBPB) or crown ether complexes such as 18-crown-6/KBr as catalysts to produce high molecular weight polymers, although the reaction occurred without any catalyst to give low molecular weight polymer in low yield at 90°C for 48 h. It was also found that the reaction proceeded smoothly in aprotic polar solvents such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc) to produce high molecular weight polymers. Polyaddition reactions of DGEBA or digylcidyl ether of ethylene glycol (DGEEG) with BBAMB, other bis(chloroacetoxy)esters or bis(bromoacetoxy)esters using TBPB in DMAc also proceeded smoothly to give the corresponding polymers. The resulting poly(ether-ester)s contain reactive halomethyl groups as side chains, which were introduced during main chain formation. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3791–3799, 1997     

Syntheses and radical ring-opening polymerization behavior of vinylcyclopropanone cyclic acetals having exomethylene and phenyl groups

Syntheses and radical ring-opening polymerizations of vinylcyclopropanone derivertives having cyclic six-membered acetal, exomethylene, and phenyl groups; 1-vinyl-6-methylene-4,8-dioxaspiro[2.5&]octane ( 2b ), 1-vinyl-5,7-dimethyl-6-methylene-4,8-dioxaspiro[2.5]octane ( 2c ), 1-vinyl-5-phenyl-4,8-dioxaspiro[2.5]octane ( 2d ), and 1-vinyl-5,7-diphenyl-4,8-dioxaspiro[2.5]octane ( 2e ), were carried out. The monomers were prepared by reactions of 1,1-dichloro-2-vinylcyclopropane and the corresponding diols in DMF in the presence of sodium hydride. Radical polymerizations of 2b – 2e were carried out at 60, 80, and 120°C in the presence of an appropriate initiator (3 mol % vs. monomer) in degassed sealed ampoules for 20 h. Although colorless transparent polymers (M̄_n 2300–13,500) were isolated by preparative HPLC for the most monomers, a crosslinked polymer was obtained in the case of 2b . The structures of the polymers were determined to consist of single and double ring-opening units. The content of the double ring-opened unit was 25–75% by comparison of IR spectra to a model compound. It is suggested that the double ring-opened propagating chain end is stabilized by the substituents on the cyclic acetal rings. The two-center energies of the cyclopropane ring and activation energy of ring-opening calculated by molecular orbital methods may explain the selectivity in the cleavage of the cyclopropane ring, and the degree of double ring-opening. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2501–2512, 1997     

ESR study on chemical crosslinking reaction mechanisms of polyethylene using a chemical agent—II. The effect of phenolic antioxidants

The effect of antioxidant on the reaction mechanism of chemical crosslinking of polyethylene (PE) with dicumyl peroxide (DCP) at high temperatures was investigated by electron spin resonance (ESR). The antioxidant reacts with the alkyl radicals in PE formed by the thermal decomposition of DCP above 120°C, and disturbs the crosslinking. A phenolic type antioxidant produced the phenoxy radical by the reaction with alkyl radicals formed in PE. It is suggested that the selection of a suitable antioxidant for PE crosslinking can be made by ESR analysis. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2431–2439, 1997     

Polymerization of N-vinylcarbazole. II. Kinetic studies on polymerizations involving azoisobutyronitrile and benzoyl peroxide

The polymerization of N-vinylcarbazole at 60°C in benzene has been initiated with azoisobutyronitrile, benzoyl peroxide, and their mixtures. The kinetics indicate that the azonitrile and the peroxide promote polymerizations of fundamentally different types. The resulting polymers have been examined by gel-permeation chromatography. The polymer produced with benzoyl peroxide contains a small amount of a high molecular weight fraction which, from the point of view of end groups, resembles the polymer made by use of the azonitrile. It is concluded that benzoyl peroxide in this system gives rise to two types of polymerization which occur simultaneously.     

Polarons radical polymerization

Polystyrene has been typically prepared with radical polymerization by benzoyl peroxide (BPO) or azobisisobutyronitrile (AIBN). In this report, polymerization of styrene was carried out by radical cations of polyaniline (PANI). Polarons of conducting polymers are consisting of radical cations. The polarons bear electrical conduction as a charge carrier. We employ the polarons as an initiator for radical polymerization. Polymerization of styrene and acrylonitrile by the polarons was conducted to explore new possibility of conducting polymers. Fourier‐transfer infrared absorption (FTIR) spectroscopy measurements for the resultant polymers obtained with polarons of polyaniline indicates that the polystyrene thus synthesized grows from polyaniline. The qualitative solubility, average molecular weight, and thermal stability are comparable to that of polystyrene obtained by the common method with BPO. Radical polymerization by polarons may provide a new avenue for radical polymerizations through application of conducting polymer. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 805–811     

Permeation and separation of benzene/cyclohexane mixtures through liquid-crystalline polymer membranes

The side-chain liquid-crystalline polymer (LCP) was synthesized by the addition of the mesogenic monomer to poly(methylsiloxane) with Pt catalyst. When the benzene/cyclohexane mixtures were permeated through the LCP membranes by pervaporation at various temperatures, the permeation rate increased with increasing benzene concentration in the feed solution and permeation temperature. Though the LCP membranes exhibited a benzene permselectivity, a mechanism of the permeation and separation for the benzene/cyclohexane mixtures was different in the glassy, liquid-crystalline and isotropic state of the LCP membranes. These results suggested that the permselectivity was fairly influenced by the change of the LCP membrane structure, that is, a state transformation. It was found that a balance of the orientation of mesogenic groups and flexibility of siloxane chains is very important for the permeability and selectivity. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 699–707, 1997     

Radical ring-opening polyaddition of a bifunctional vinylcyclopropane bearing a spiroacetal moiety with dithiols

Radical polyadditions of vinylcyclopropane having spiroacetal moiety, 1,10-divinyl-4,8,12,15-tetraoxatrispiro[2.2.2.2.2.2] pentadecane ( 1 ), and various dithiols were examined. 1 was prepared by the reaction of 1,1-dichloro-2-vinylcyclopropane and pentaerythritol, and radical polyadditions of 1 and dithiols were carried out at 60 and 120°C for 20 h in the presence of an appropriate initiator (3 mol % vs. 1 ) in degassed sealed ampoules or at 20°C under photo irradiation by using a 400 W high-pressure mercury lamp. Poly( 1 ), pale yellow transparent viscous polymers was isolated by reprecipitation with ether containing a small amount of triethylamine to avoid hydrolysis of the polymer. The obtained polymers were soluble in chlorobenzene, DMF, and chloroform but insoluble in ether and n-hexane. The molecular weights of the polymers obtained from aliphatic dithiols were smaller than those from aromatic ones. The structure of the polymer was determined by comparing the NMR spectra with those of the model compounds, which were obtained by radical addition of 1 and benzyl mercaptan. The reaction proceeded through radical polyaddition of dithiol to 1 via radical ring-opening polymerization of the cyclopropane ring. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2487–2492, 1997     

Syntheses and radical polymerizations of optically active (meth)acrylamides having amino acid moieties

Syntheses and radical polymerizations of several (meth)acrylamides having L -amino acid moieties were examined. The monomers were prepared by the reactions of L -amino acid ester hydrochlorides with (meth)acryloyl chloride in the presence of triethylamine in satisfactory yields. Radical polymerizations of the monomers were carried out in the presence of AIBN (1 mol %) in bulk and in several solvents to afford the corresponding polymers in satisfactory yield. The glass transition temperatures and specific rotations of the polymers depended on the substituents of the L -amino acid moieties. Nearly the same specific rotations were observed for the monomers and the model compounds of the polymer units, N-pivaloyl amino acid methyl esters. On the contrary, the specific rotations of the polymers shifted to the negative direction in ca. 30°. The interaction between the polymer side chains might affect the changes in the specific rotations from monomers to polymers. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2619–2629, 1997     

Photopolymerization of methyl methacrylate with the use of morpholine-chlorine charge transfer complex as the photoinitiator

Polymerization of methyl methacrylate (MMA) was kinetically studied under photo condition using near UV visible light at 40°C and employing morpholine (MOR)–chlorine (Cl₂) charge transfer (C-T) complex as the photoinitiator. The rate of polymerization (R_p) was dependent on morpholine/chlorine mole ratio; the 1 : 2 (MOR–Cl₂) C-T complex acted as the latent initiator complex, C, which underwent further complexation with the monomer molecules to give the actual initiator complex, I. Using 1 : 2 (MOR-Cl₂) C-T complex as the latent initiator, the initiator exponent evaluated for bulk photopolymerization of MMA was 0.071 and monomer exponent determined from studies of photopolymerization in benzene diluted system was 1.10. Benzoquinone behaved as a strong inhibitor and the polymers tested positive for the incorporation of chlorine atom end groups. Polymerization followed a radical mechanism. Kinetic nonideality as revealed by low (≪0.5) initiator exponent and a monomer exponent of greater than unity were explained in terms of primary radical termination effect. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1681–1687, 1997     

Spacer‐length‐dependent association in polymers with multiple‐hydrogen‐bonded end groups

Herein, we investigate the influence of spacer length on the homoassociation and heteroassociation of end‐functionalized hydrogen‐bonding polymers based on poly(n‐butyl acrylate). Two monofunctional ureido‐pyrimidinone (UPy) end‐functionalized polymers were prepared by atom transfer radical polymerization using self‐complementary UPy‐functional initiators that differ in the spacer length between the multiple‐hydrogen‐bonding group and the chain initiation site. The self‐complementary binding strength (K_dim) of these end‐functionalized polymers was shown to depend critically on the spacer length as evident from ¹H NMR and diffusion‐ordered spectroscopy. In addition, the heteroassociation strength of the end‐functionalized UPy polymers with end‐functionalized polymers containing the complementary 2,7‐diamido‐1,8‐naphthyridine (NaPy) hydrogen‐bond motif is also affected when the aliphatic spacer length is too short. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis,polymerization, and isomerization of isoimide containing acrylate esters

Several isoimides substituted with hydroxylated substituents were prepared, and allowed to react with acryloyl chloride to form the corresponding acrylate esters. The acrylates were polymerized free radically using AIBN as the initiator yielding medium molecular weight polyacrylates. Upon warming the prepared polyacrylates or treatment with base most of the isoimide pending groups rearranged to the stable form of the corresponding imides. These rearrangements were accompanied by increase in softening points of the polymers forming thermally more stable resins. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3125–3130, 1997