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In this work, semi-interpenetrating gels of poly(N-isopropyl acrylamide) and methylcellulose were successfully synthesized by using the Frontal Polymerization (FP) technique. The gels were obtained in the presence of dimethyl sulfoxide and trihexyltetradecylphosphonium persulfate, as polymerization solvent and radical initiator, respectively, hence avoiding the formation of bubbles during polymerization. Then, some of the gels containing dimethyl sulfoxide were thoroughly washed with water, hence obtaining the corresponding hydrogels. The effects of the ratio between poly(N-isopropyl acrylamide) and methylcellulose, the amount of crosslinker and solvent medium (i.e. dimethyl sulfoxide and water) were thoroughly studied, assessing the influence of temperature and velocity of FP fronts on the glass transition temperature values (dried samples), on the swelling behavior and on the dynamic-mechanical properties (gels swollen both in water and dimethyl sulfoxide).

Polydiolcitrates are an emerging class of biocompatible polyesters with a great potential in the field of biomedicine and packaging for food and drug materials. In this work, a new type of (co-)polydiolcitrates made of citric acid (CA) and ethylene glycol (EG) and/or poly(ethylene glycol) (PEG) is investigated. By varying both the EG/PEG and the CA/diol molar ratios, materials exhibiting very different swelling behavior, mechanical and thermal properties are obtained. In particular, the substitution of EG segments with longer and flexible PEG ones results in an increase in crosslinking density, with remarkable effects on swelling capacity, glass transition temperature, and Young modulus. Moreover, polyesters with CA/diol molar ratio equal to 1:1 exhibit shape memory properties, with full capacity of keeping the temporary shape and high capacity of recovering the original shape. This work demonstrates that the appropriate choice of polyester composition allows modulating the sample properties, that permits to these materials to cover a wide range of possible applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3713–3720

Frontal polymerization was successfully used to synthesize copolymer hydrogels of poly(N-vinylcaprolactam-co-itaconic acid). All materials were characterized by response to stimuli (pH and/or temperature), depending on the itaconic acid content. Namely, relatively low amounts of this latter were found to be crucial for determining the degree of swelling. In particular, hydrogels behave differently if swollen at pH values that are higher or lower of 7–8, and exhibit temperature response as well (lower critical solution temperature at ca. 30 °C), which makes these materials potentially interesting for biomedical applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2166–2170

The frontal ring opening metathesis polymerization (FROMP) of dicyclopentadiene (DCPD) in the presence of limonene, using second generation Grubbs’ catalysts, is reported. The effect of limonene on the amount of catalyst and the typical frontal polymerization parameters, as maximum temperature (Tmax) and velocity of the front (Vf), is studied. In addition, the influence of limonene on the mechanical properties of the polymeric samples is reported. Finally, a deep study on the swelling properties of polymers is done. It has been demonstrated that limonene acts as both inhibitor and solvent of the catalyst. The Tmax, Vf, Tg, and Young modulus values decrease as the amount of limonene increases, and the polymer samples swell in THF depending on the amount of limonene. All results indicate that the limonene addition on FROMP of results in advantages on the polymerization reaction and its parameters and on the final polymer properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 63–68

Frontal polymerization (FP) of poly(ethylene glycol) diacrylate (PEGDA) was carried out using benzoyl peroxide (BPO) as radical initiator. In addition, a pyrene containing monomer, 1-pyrenebutyl acrylate (PyBuAc), was incorporated as a fluorescent probe in order to obtain luminescent materials with different chromophore contents. The resulting polymers were characterized by FT-IR spectroscopy in the solid state and their thermal properties were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Moreover, the optical properties of these materials were studied by absorption and fluorescence spectroscopy. The maximum amount of the incorporated pyrene-containing monomer into the polymer matrix was limited to 1 wt % by the polymerization process. The obtained labeled polymers poly(PEGDA-co-PyBuAc) exhibited a broad absorption band at 345 nm. The fluorescence spectra of these polymers exhibited mainly “monomer emission” so that no excimer emission was observed. It is possible to tune the color of the emitted light by varying the pyrene content in the samples. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2890–2897

The frontal ring opening metathesis polymerization of dicyclopentadiene using first and second generation Grubbs' catalysts is reported. To have sufficiently long pot lives, dimethylaminopyridine is added as an inhibitor. By choosing the proper compositions, it is possible to determine the ranges in which pure frontal polymerization occurs. A thorough study on the effect of the above components on the maximum temperatures reached by the front and on its velocities is performed. Namely, temperatures range from 164 to 205 °C depending on the type of catalyst and the above component ratios. Besides, front velocities range from 1.0 to 15.0 cm/min, which are one of the lowest and one of the highest values reported so far in any frontal polymerization experiment reported in literature. This finding allows the complete control of the frontal ring opening polymerization of dicyclopentadiene also in practical applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2776–2780

Novel polyacrylamide-based hydrogels containing3-(trimethoxysilyl)propyl methacrylate and/or tetraethoxy silanewere synthesized by means of frontal polymerization, usingammonium persulfate as initiator, N,N 0 -methylene bisacryla-mide as crosslinking agent and dimethyl sulfoxide as solvent.The obtained samples were treated at pH of 2 or 5 to inducethe sol–gel reaction and evaluate their swelling behavior in theconditions. The occurrence of this reaction was assessed bysolid-state NMR. Moreover, the thermal properties of the drymaterials were studied by differential scanning calorimetry andthermal gravimetric analysis, and their water-contact angleswere measured. It was found that the amount of Si affects theextent of swelling and the hydrophilicity of the resulting mate-rials. V C 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A:Polym. Chem. 2013, 51, 4618–4625 KEYWORDS: acrylic polymers; frontal polymerization; hydrogels;interpenetrating networks (IPN); radical polymerizationINTRODUCTION

The frontal polymerization (FP) of bisphenol A ethoxylate diacrylate (BPAEDA) was carried with and without the presence of two different azobenzene comonomers by means of an external heating source. The first azomonomer (MDR-1) is a derivative of disperse red-1, N-ethyl-N-(2-hydroxyethyl)-4-(4-nitrophenylazo)aniline, whereas the second (E)-2-(4-((4-nitrophenyl)diazenyl)phenyl)-5,8,11-trioxa-2-azatridecan-13-yl methacrylate (4PEGMAN) comes from the azo-dye N-methyl-N-{4-[(E)-(4-nitrophenyl)diazenyl]phenyl}-N-(11-hydroxy-3,6,9-trioxaundecas-1-yl) amine. In this work, an ionic liquid trihexyltetradecylphosphonium persulfate was used as initiator. This compound produced stable propagating polymerization fronts with good velocities and moderate maximum temperature values. Moreover, this initiator prevented bubble formation and was found to be the most efficient when it was used in lower amounts with respect to other initiators, such as benzoyl peroxide, 2,2′-azobisisobutyronitrile, aliquat persulfate®, and tetrabutylphosphonium persulfate. The thermal properties of the obtained polymers and copolymers were determined by thermogravimetric analysis and differential scanning calorimetry. The nonlinear optical (NLO) characterizations of the developed BPAEDA/MDR-1 and BPAEDA/4PEGMAN copolymers were performed according to the Z-Scan technique in film samples prepared by classical polymerization. It has been proven that samples with higher 4PEGMAN content (0.26 mol %) exhibited outstanding cubic NLO-activity with positive NLO-refractive coefficients in the promising range of n2 = +3.2 × 10−4 esu. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

In this work, we report on the synthesis and charac- terization of homopolymers and copolymers of acrylic acid and 2-hydroxyethyl acrylate prepared by the use of the frontal poly- merization (FP) technique. Tetraethyleneglycoldiacrylate was used as a crosslinker and benzoyl peroxide as an initiator. The maximum temperatures reached by the front were in the range between 214 � C and 296 � C. Besides, front velocities ranged between 3.9 and 10.8 cm/min, the latter being one of the high- est values reported so far in the FP literature. Differential scan- ning calorimetry was used to estimate the conversion degree, which was always comprised between 90% and 96%, and to determine the glass transition temperatures, which were found to be dependent on the composition, with values ranging from 13 � C to 168 � C. Moreover, the obtained materials were allowed to swell in aqueous solutions at various pH. The samples ex- hibit a moderate increase of the swelling ratio percentage (SR%) at pH � 5-6, and a sudden and larger SR% increase at pH � 12-13 depending on the composition, thus indicating the obtainment of pH-responsive polymer hydrogels. V C 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 1515- 1520, 2012

Phenoxyethyl acrylate (2-PEA) was polymerized alone and in the presence of an azobenzene comonomer derived from Disperse Red-1, N-ethyl-N-(2-hydroxyethyl)-4-(4-nitropheny- lazo)aniline (MDR-1), by using the frontal polymerization tech- nique. Two novel ionic liquids, recently synthesized by us, were used as initiators: tetrabutylphosphonium persulfate (TBPPS) and trihexyltetradecylphosphonium persulfate (TETDPPS). Even if their concentrations were smaller than those found when ben- zoyl peroxide and terbutylperoxy neodecanoate were used, these compounds gave rise to stable propagating polymerization fronts characterized by relatively low maximum temperatures and good velocities. Moreover, at variance to these latter, TBPPS and TETDPPS prevent bubble formation, thus allowing the use of the obtained materials in optical applications. The obtained polymers were characterized by infrared spectroscopy (FTIR), their thermal properties were determined by differential scanning calorimetry, and their optical properties were studied by absorption spectros- copy in the UV-vis region. Finally, the nonlinear optical (NLO) properties of the 2-PEA/MDR-1 copolymers obtained with TBPPS and TETDPPS were performed according to the Z-Scan technique with prepared film samples. It has been proven that samples with higher MDR-1 content (0.05 mol %) exhibited outstanding cubic NLO activity with negative NLO refractive coefficients around n2 ¼� 1.7 � 10 � 3 esu. V C 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 821-830, 2012

Super water absorbent polymer hydrogels were syn- thesized by frontal polymerization. These materials were obtained by copolymerizing N-isopropyl acrylamide (NIPAAm) and 3-sulfopropyl acrylate potassium salt (SPAK) in the pres- ence of N,N 0 -methylene-bis-acrylamide as a crosslinker. It was found that their swelling behavior in water can be easily tuned by using either the appropriate monomer ratio or the amount of the crosslinker used. Namely, the swelling ratio was found to range from about 1000% for the NIPAAm homopolymer in the presence of 5.0 mol % of crosslinker, up to 35,000% for the sam- ple containing 87.5 mol % of SPAK and 1.0 mol % of crosslinker. The affinity toward water was also confirmed by contact angle analysis. Moreover, the obtained hydrogels exhibit a thermo- responsive behavior, with a lower critical solution temperature of about 28-30 � C. This value is close to that of poly(NIPAAm) but with a swelling capability that dramatically increases as the amount of SPAK increases. V C 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 1228-1234, 2011

In this work, a new stimuli-responsive composite polymer hydrogel containing partially exfoliated graphite was prepared by frontal polymerization. The materials obtained were characterized by differential scanning calorimetry, RAMAN, scan electron microscopy, transmission electron microscopy, atomic force microscopy, and in terms of swelling behavior. It was found that the maximum temperature reached by the polymerization front and the lower critical solution temperature are affected by the graphite content.

The syntheses of hybrid epoxy resins made from different ratios among bisphenol-A diglycidyl ether, 3-glycidoxypropyltrimethoxysilane (GPTMS), and diethylenetriamine were successfully performed by using frontal polymerization. Conversions were always almost quantitative, and, because of the use of this alternative convenient technique, materials were prepared in very short times. Samples were characterized by DSC, TGA, IR spectroscopy, and solvent extraction. It was found that those materials containing a relatively high-Si amount exhibit two different transition temperatures, with the highest one that increases as the content of GPTMS raises. The analogies and the differences with the analogous samples prepared by the classical batch technique are discussed.

Frontal polymerization was used as an alternative technique for the preparation of super water absorbent hydro- gels obtained from acrylamide and 3-sulfopropyl acrylate, po- tassium salt (SPAK) in the presence of N,N 0 -methylene- bisacrylamide as a crosslinker. All samples were synthesized in dimethyl sulfoxide, and their swelling behavior in water was investigated. It was found that their features are dependent on the monomer ratio used, which influenced the porous mor- phology, and consequently, the swelling capability. The swel- ling ratio ranges from about 1000% for the acrylamide homopolymer up to 14,000% for the sample containing 87.5 mol % of SPAK, thus indicating that this parameter can be easily tuned by using the appropriate monomer ratio. The affinity towards water was eventually confirmed by contact angle analysis. Polymer hydrogels made from at least 62.5 mol % SPAK exhibit a thermoresponsive behavior, with a lower critical solution temperature of � 30 � C. V C 2010 Wiley Periodi- cals, Inc. J Polym Sci Part A: Polym Chem 48: 2486-2490, 2010

We studied the frontal curing of trimethylolpropane triglycidyl ether (TMPTGE) using two BF3-amine initiators and two fillers, kaolin and fumed silica. In the case of kaolin, the range of concentrations allowing for frontal polymerization to propagate was dependent on its heat absorption effect whereas in the case of silica it was a consequence of the rheo- logical features of this additive. However, for both systems the velocity and front temperature show the same trends; in all cases front velocities were on the order of 1 cm/min with front temperatures about 200 C. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2000-2005, 2010

This work deals with the preparation of poly(urethane acrylates) by using two different polymerization techniques. Namely, the classical batch procedure has been compared with frontal polymerization (FP). A thorough study on the effect of initiator type, concentration, and on the velocity of the front and its maximum temperature has been carried out. Moreover, two different synthetic ways have been studied: the one step poly(urethane acrylate) preparation starting directly from 1,6 diisocyanato hexane and 2-hydroxyethyl acrylate, and the two step procedure consisting of the synthesis of the corresponding diurethane diacrylate and of its subsequent polymerization. The first method has the advantage of being faster but some caution is necessary due to the excessive heat that is generated if the reaction conditions are not properly chosen. The second approach requires a further step but has the advantage of being more controlled. DSC analysis did not show any significant difference by comparing the thermal properties of the materials obtained by the two techniques (batch and FP). However, since FP runs are very easy and fast to be performed, FP should be seriously taken into proper account when these materials have to be prepared.

Frontal polymerization (FP) has been successfully applied, for the first time, to obtain polymeric nanocomposites containing polyhedral oligomeric silsesquioxanes (POSS) in an amine-cured epoxy matrix. Variations of maximum temperature ( T max ) and front velocity ( V f ) have been studied. A comparison of these products with the corresponding materials, obtained by the classical batch polymerization technique, demonstrated that FP allows a higher degree of conversion than batch polymerization. The products have been characterized in terms of their thermal behavior with DSC analysis. SEM and X-ray analyses revealed the morphology and the structures of the nanocomposites. The nanocomposites obtained by FP have the same characteristics of those synthesized, in much longer times, by batch polymerization.

By combining frontal polymerization and radical-induced cationic polymerization, it was possible to cure thick samples of an epoxy monomer bleached by UV light. The effect of the relative amounts of cationic photoinitiator and radical initiator was thoroughly investigated and was related to the front's velocity and its maximum temperature. The materials obtained were characterized by quantitative conversion also in the deeper layers, not reached by UV light.

A new series of linear and crosslinked copolymers, obtained from 3-octyl-1-vinylimidazolium bromide (VImBr) and N-isopropylacrylamide (NIPAAm), were prepared by radical polymerization. Namely, VImBr was synthesized from 1-bromooctane and an ionic liquid such as 1-vinylimidazole. NIPAAm was used because it gives raise to well known ther- moresponsive (co-)polymers. The copolymers were thoroughly characterized by means of 1 H NMR and 13 C NMR spectroscop- ies. Besides, differential scanning calorimetry, Fourier trans- form infrared spectroscopy, and scanning electron microscopy were also used. Moreover, the swelling behavior and the ther- moresponsive properties of the corresponding hydrogels were studied. It was found that the VImBr incorporation into the copolymers does have a dramatic influence on both the ther- mal properties of the dried materials and the lower critical solution temperature of the corresponding hydrogels. In detail, the glass transition temperature was dependent on the mono- mer ratios, and ranged from 5 to 155 � C. Analogously, the lower critical solution temperature of the resulting hydrogels ranged from less than 10 up to 38 � C, thus including the physi- ological temperature. NMR spectroscopies, which were per- formed on the linear polymers, indicated that the monomers exhibit an alternating tendency resulting in a microstructure in which blocks are not present, at least when the two monomers are in equimolar amounts. V C 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3521-3532