Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• materials used in additive manufacturing. It is also compatible to a photopolymerization process. For example, it can be applied to the photo-3D-printing of silicone resin [83]. The refractive index is one of the most important optical properties and researchers have invested plenty of effort to develop

• couplings in PATs. Scheme 10 redrawn from [79]. General thiol-ene photopolymerization process. Scheme 11 redrawn from [81]. (a) Three generations of Grubbs catalysts. (b) Proposed mechanism for photo-ROMP via a reductive quenching pathway and (c, d) chemical structures of the (c) initiators and (d) monomers

An initiator- and catalyst-free hydrogel coating process for 3D printed medical-grade poly(ε-caprolactone)

• Jochen Löblein,
• Thomas Lorson,
• Miriam Komma,
• Tobias Kielholz,
• Maike Windbergs,
• Paul D. Dalton and
• Robert Luxenhofer

Beilstein J. Org. Chem. 2021, 17, 2095–2101, doi:10.3762/bjoc.17.136

• photopolymerization for the hydrophilic modification of microfiber scaffolds obtained from hydrophobic medical-grade poly(ε-caprolactone) via melt-electrowriting. Contact angle measurements and Raman spectroscopy confirms the formation of a more hydrophilic coating of poly(2-hydroxyethyl methacrylate). Apart from

• surface modification, we also observe bulk polymerization, which is expected for this method, and currently limits the controllability of this procedure. Keywords: additive manufacturing; light-induced polymerization; self-initiated photografting and photopolymerization; surface-initiated polymerization

• achieved with self-initiated photografting and photopolymerization (SIPGP, Scheme 1). SIPGP is a simple, solvent-free bulk/surface photografting first introduced by Deng et al. grafting maleic anhydride [20] and styrene [21] onto low-density poly(ethylene) films. Later, this was extended for other monomers

Towards new NIR dyes for free radical photopolymerization processes

• Haifaa Mokbel,
• Guillaume Noirbent,
• Didier Gigmes,
• Frédéric Dumur and
• Jacques Lalevée

Beilstein J. Org. Chem. 2021, 17, 2067–2076, doi:10.3762/bjoc.17.133

• polymerization of acrylate/epoxy monomer blends) can also be carried out upon NIR light with the proposed systems. Keywords: cyanine; NIR light; photochemistry; Introduction Photopolymerization processes are well established due to the specific features and advantages. Indeed, the reaction is carried out at

• acrylate function conversion (FC) measured were higher than 80%. Such a high reactive function conversion is quite high for multifunctional monomers (with PETIA being a trifunctional acrylic monomer). Moreover, for the majority of the proposed systems, the photopolymerization starts as soon as the light is

• turned on. This can be explained by a low oxygen inhibition, which is an advantage for different applications where the photopolymerization under air is required. As shown in Figure 2 and Figure 3, only CNa, CBPh3, CI3, and CI10 show a long inhibition time, and this can be ascribed to the low absorption

Photoinduced post-modification of graphitic carbon nitride-embedded hydrogels: synthesis of 'hydrophobic hydrogels' and pore substructuring

• Cansu Esen and
• Baris Kumru

Beilstein J. Org. Chem. 2021, 17, 1323–1334, doi:10.3762/bjoc.17.92

• the arbitrary photopolymerization process. In addition, we were not able to identify free polymer chains during the purification process, which indicates a covalent growth of polymers on a hydrogel host. It is expected that pore modification on networks will influence the thermal stability of the

• and left for 2 hours to complete adsorption–desorption equilibrium. After 2 hours, monomer swollen hydrogel was replaced into another capped glass vial and set between two visible light sources (10 cm distance each) overnight to accomplish photopolymerization. Afterwards, it was purified by immersing

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• reactions, including photopolymerization, photohydrolysis, and photodimerization [42][43][44][45][46]. Chemical transformations assisted by nanosized reaction vessels have gained attention in the field of supramolecular photocatalysis. Therefore, Sivaguru et al. performed the photodimerization of coumarin

• ) photopolymerization under visible-light irradiation in an aqueous solution [48]. Briefly, the supramolecular PDI–CB[7] complex in Figure 15 acts as a photocatalyst at a low concentration (1 ppm relative to the monomer), which could be utilized for the preparation of a series of homo- or block copolymers with an

• this supramolecularly driven photopolymerization (0.0305 min−1) could be enhanced by decreasing the aggregation of PDI via host–guest interactions. Recently, Wang and co-workers fabricated the orthogonal supramolecular ternary self-assembled system 27@CB[7]/EY via host–guest interactions between CB[7

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• then kept constant or slightly decreased. The possible initiation of the polymerization is presented in Scheme 11, where hydrogen bonding of 36 with water is crucial. In 2013, Wang and co-workers also reported the use of aliphatic ketones and aldehydes as photoinitiators for the photopolymerization of

• carried out, indicating that the polymerization of MAA (42) was mainly induced by photoinitiation by the aliphatic ketones 44 or formaldehyde (35), rather than by self-initiation of the monomer. Furthermore, oxygen was shown to strongly inhibit the photopolymerization, and an increase in the UV intensity

• than acetone (4). The authors proposed that the photoinitiation mechanism for the photopolymerization of aliphatic ketones or aldehydes was similar to the one concerning photografting, and the mechanism is presented in Scheme 12 [42][44]. While the aliphatic ketones 44 did not exhibit photoinitiation

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• this point of view outstanding properties since the aforementioned benefits enabled their use in photopolymerization to pattern light sensitive coatings [11][12][13][14], to cure liquid coatings [15], and powder coatings [16][17] or to initiate either a chemical and/or thermal curing process [58

• their use in applications based on sensitized photoinduced electron transfer. This can be NIR-sensitized photopolymerization resulting in formation of initiating radicals and conjugate acid [5][6][13][14][15][63][64]. Recently, the use of NIR-LEDs exhibiting high excitation intensity brought more light

• “molecular oven/furnace” in heat-based physical and/or chemical processes. There, they can generate heat in an ON/OFF procedure on demand [58]. Many examples of cyanines focus on the use of absorption in the NIR [64]. Among of the disclosed applications, photopolymerization depicts one representative method

Dyes in modern organic chemistry

• Heiko Ihmels

Beilstein J. Org. Chem. 2019, 15, 2798–2800, doi:10.3762/bjoc.15.272

• dyes also contribute as essential components in modern applications such as in OLEDs [5][6], solar cells [7][8], organic semiconductors [9], NLO materials [10], photopolymerization [11], or Chemistry 4.0 [12]. From its very beginning, dye chemistry is strongly connected to the scientific developments

A photochemical determination of luminescence efficiency of upconverting nanoparticles

• Baptiste Amouroux,
• Clément Roux,
• Jean-Claude Micheau,
• Fabienne Gauffre and
• Christophe Coudret

Beilstein J. Org. Chem. 2019, 15, 2671–2677, doi:10.3762/bjoc.15.260

• can find applications in material sciences such as photopolymerization [8], or micellization photocontrol [9], since the excitation wavelength lies in the first transparency window of most biological media, a spectacular range of use in biological sciences has been explored from drug release [10

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• networks. Keywords: photoinitiator; photopolymerization; photoredox catalysis; photoredox catalyst; Introduction Photopolymerization reactions are now widely used both in industry and in academic laboratories. These processes usually lead to the transformation of a liquid resin in a 3D solid polymer upon

• “on-off” aspect of a lamp offers good possibilities of external regulator of the reaction. Another advantage is the spatial control, i.e., the reaction only occurs in the light-irradiated areas. For all these advantages, photopolymerization reactions are already encountered for applications in a lot

• of sectors such as coatings, adhesives, paints, inks, composites, 3D-printing, dentistry, data storage ... [5][6][7]. Review 1 Photopolymerization processes and uses of photocatalysts (PCs) Traditionally, polymer manufacturing is made through thermal curing. However, this route has many limitations

Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates

• Vladimir A. Burilov,
• Guzaliya A. Fatikhova,
• Mariya N. Dokuchaeva,
• Ramil I. Nugmanov,
• Diana A. Mironova,
• Pavel V. Dorovatovskii,
• Victor N. Khrustalev,
• Svetlana E. Solovieva and
• Igor S. Antipin

Beilstein J. Org. Chem. 2018, 14, 1980–1993, doi:10.3762/bjoc.14.173

• distortion of their backbone. They can be easily prepared through photopolymerization of supramolecularly assembled diacetylenes [49]. The functionalization of a PDA matrix with appropriate receptor fragments offers the possibility to sense various analytes by naked-eye detection. Noncovalent doping of

• diacetylene surfactant matrix by amphiphilic receptors with subsequent photopolymerization is a commonly used approach for the design of colorimetric analytical devices [50]. Taking into account the cationic nature of the synthesized calixarene macrocycles, the amido-diacetylene lipid bearing a terminal amino

• means that the addition of the non-polymerizable calixarene 10b to AEPCDA results in an increase of the diacetylene photopolymerization degree. This effect is quite unusual and can be associated with the change of the vesicles packing upon the addition of 10b and the formation of higher organized

Highly reactive, liquid diacrylamides via synergistic combination of spatially arranged curing moieties

• Maximilian Maier,
• Magnus S. Schmidt,
• Markus Ringwald and
• Christoph P. Fik

Beilstein J. Org. Chem. 2017, 13, 372–383, doi:10.3762/bjoc.13.40

• synergistic combination of optimally arranged functional groups could be identified. The highest possible level of intramolecular synergism was found for low viscous N,N'-diacryloyl-N,N'-diallyl-1,4-but-2-enediamine. Keywords: acrylamide; allyl; cyclopolymerization; photopolymerization; spatial effect

• 3). In order to verify an assumed, underlying cyclopolymerization mechanism, FTIR spectra of the crosslinkers were recorded before and after photopolymerization (Figure 6). All compounds containing both, acrylamido and allyl functions (1, 3–5), showed two peaks for the acrylamide vibration at ≈1645

Investigations of thiol-modified phenol derivatives for the use in thiol–ene photopolymerizations

• Sebastian Reinelt,
• Monir Tabatabai,
• Urs Karl Fischer,
• Norbert Moszner,
• Andreas Utterodt and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 1733–1740, doi:10.3762/bjoc.10.180

• flexural strength and modulus of elasticity is twice as high compared to the PETMP reference system. Keywords: composites; crosslinking; dental polymers; high performance polymers; photopolymerization; Introduction Restorative composites consist of a polymerizable organic matrix (10–60 wt %) and

Tailoring of organic dyes with oxidoreductive compounds to obtain photocyclic radical generator systems exhibiting photocatalytic behavior

• Christian Ley,
• Julien Christmann,
• Ahmad Ibrahim,
• Luciano H. Di Stefano and
• Xavier Allonas

Beilstein J. Org. Chem. 2014, 10, 936–947, doi:10.3762/bjoc.10.92

• transfer; kinetic; photocatalysis; photochemistry; photocyclic initiating system; photopolymerization; photoredox catalysis; radical generator; Introduction Among the possible usage of light, the conversion of photons into chemical energy, as stored into radicals or ions, is of great interest. As a part

• development of new methods for organic synthesis was achieved by use of photolabile protective groups, which could be released under irradiation by light [10][11]. Since many decades in industry, PRG are used in photopolymerization, a field in which the PRG prompt the initiation of the polymerization through

• a chain reaction [12]. Photopolymerization was first used over 4000 years ago in the mummification process [13]. During the last decades the number of commercial applications is still continuously increasing. By example, photopolymer applications are found in electronic materials [14], printing

Metal and metal-free photocatalysts: mechanistic approach and application as photoinitiators of photopolymerization

• Jacques Lalevée,
• Sofia Telitel,
• Pu Xiao,
• Marc Lepeltier,
• Frédéric Dumur,
• Fabrice Morlet-Savary,
• Didier Gigmes and
• Jean-Pierre Fouassier

Beilstein J. Org. Chem. 2014, 10, 863–876, doi:10.3762/bjoc.10.83

• -trapping, laser flash photolysis, steady state photolysis, cyclic voltammetry and luminescence experiments. Keywords: LEDs; photoinitiators; photopolymerization; photoredox catalysis; Introduction Photoredox catalysis is now well-known and largely used in organic synthesis, especially in the development

• introduced into the polymer photochemistry field (area) in the very past years (see a review in [15][16][17][18][19][20][21][22]). Indeed, in this area, free-radical photopolymerization (FRP, Scheme 1, reactions 1 and 2), cationic photopolymerization (CP, Scheme 1, reactions 3 and 4), free-radical promoted

• cationic photopolymerization (FRPCP, Scheme 1, reactions 5–7) or acid and base-catalyzed photocrosslinking (reactions 8 and 9) are initiated using photoinitiators (PI) which generate reactive species (radicals, cations, anions, radical cations, acids, bases). These PIs are often incorporated into

Organotellurium-mediated living radical polymerization under photoirradiation by a low-intensity light-emitting diode

• Yasuyuki Nakamura and
• Shigeru Yamago

Beilstein J. Org. Chem. 2013, 9, 1607–1612, doi:10.3762/bjoc.9.183

• -emitting diode; living radical polymerization; organotellurium compound; photopolymerization; tellurium; visible light; Introduction Living radical polymerization (LRP) is one of the most powerful methods for the synthesis of structurally well-defined polymers because of its robustness and high

• procedure for photopolymerization: A solution of MMA (1.0 mL, 9.4 mmol), 1 (16.5 μL, 0.094 mmol), and dimethyl ditelluride (10.0 μL, 0.094 mmol) was irradiated with a 6 W white LED equipped with a 20% ND filter at 70 °C for 4 h under a nitrogen atmosphere in a capped tube (Figure 3). A small portion of the

• ). The percentages in the legend refer to the ND filters used. Experimental setup for the photopolymerization using the LED. Photopolymerization in the presence of organotellurium chain transfer agent 1. Activation and deactivation mechanism of dormant (P-TeMe) and ditelluride. Photopolymerization of MMA

New core-pyrene π structure organophotocatalysts usable as highly efficient photoinitiators

• Sofia Telitel,
• Frédéric Dumur,
• Thomas Faury,
• Bernadette Graff,
• Mohamad-Ali Tehfe,
• Didier Gigmes,
• Jean-Pierre Fouassier and
• Jacques Lalevée

Beilstein J. Org. Chem. 2013, 9, 877–890, doi:10.3762/bjoc.9.101

• application of two- and three-component photoinitiating systems (different Co_Pys with the addition of iodonium or sulfonium salts, alkyl halide or amine) was investigated in detail for cationic and radical photopolymerization reactions under near-UV–vis light. The proposed compounds can behave as new

• experiments. The mechanisms involved in the initiation step are discussed, and relationships between the core structure, the Co_Py absorption property, and the polymerization ability are tentatively proposed. Keywords: cationic photopolymerization; free-radical-promoted cationic photopolymerization

• ; photocatalysts; photoinitiators; radical photopolymerization; Introduction Free radical sources are encountered in various areas such as organic chemistry, biochemistry and polymer chemistry. In the field of polymer photochemistry applied to photopolymerization reactions, they are referred to as photoinitiators

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• (Figure 5, Table 3). Imidazoles 12 (DIYSP, δ = 41 GM, [38][39]) and 13 (FD3, δ = 1556 GM, [40]) were developed as two-photon absorbing and fluorescent A-π-A’ chromophores, which undergo photopolymerization or can be applied as fluorescent sensors for (homo)cysteine. Donor 4,5-disubstituted imidazole

Exceptionally small supramolecular hydrogelators based on aromatic–aromatic interactions

• Junfeng Shi,
• Yuan Gao,
• Zhimou Yang and
• Bing Xu

Beilstein J. Org. Chem. 2011, 7, 167–172, doi:10.3762/bjoc.7.23

• 2.5 to 2.9 ppm (Figure S1, Supporting Information File 1), photopolymerization or photodimerization are unlikely. Furthermore, the result shown in Figure S2 (Supporting Information File S2) also supports the contention that heating is insufficient to cause conversion of the trans-isomer to the cis

Synthesis, characterization and photoinduced curing of polysulfones with (meth)acrylate functionalities

• Cemil Dizman,
• Sahin Ates,
• Lokman Torun and
• Yusuf Yagci

Beilstein J. Org. Chem. 2010, 6, No. 56, doi:10.3762/bjoc.6.56

• in detail and covered by several review articles [13][14][15]. Photopolymerization is a frequently used process for the conversion of the multifunctional monomers into insoluble networks which are effective in various industrial fields such as, films, inks, coatings; photoresists, etc. [14]. The

• is due to the additional acrylate and methacrylate moieties incorporated. Kinetic studies concerning photopolymerization of the macromonomers were performed by photo-DSC. The results are shown in Figure 3 and Figure 4. The rate of photopolymerization vs. time plots for both PSU-DA-2000 and PSU-DM

• are solid at room temperature, free standing films can easily be prepared. The photopolymerization under these conditions leads to a suppressed center of coil diffusion resulting in rapid auto acceleration [28]. The results also indicate that conversions are lower than 50%. Although the oligomers

Synthesis of bis(3-{[2-(allyloxy)ethoxy]methyl}-2,4,6-trimethylbenzoyl)(phenyl)phosphine oxide – a tailor-made photoinitiator for dental adhesives

• Norbert Moszner,
• Iris Lamparth,
• Jörg Angermann,
• Urs Karl Fischer,
• Frank Zeuner,
• Thorsten Bock,
• Robert Liska and
• Volker Rheinberger

Beilstein J. Org. Chem. 2010, 6, No. 26, doi:10.3762/bjoc.6.26

• photopolymerization of dimethacrylate resins, dental adhesives or composites and undergo an α-cleavage with the formation of benzoyl and germyl radicals, which may initiate the free-radical polymerization of the monomers present. In addition, bisacylphosphine oxides, such as commercially available bis(2,4,6

• side compound by repeated column chromatography would be very difficult and expensive. However, it will probably show similar photochemical properties compared to WBAPO and therefore its separation is not necessary. Properties of WBAPO, photopolymerization and adhesives WBAPO is a liquid that exhibits

• photopolymerization of a common dental dimethacrylate resin based on mixtures of Bis-GMA (42 wt %), UDMA (37 wt %), TEGDMA (21 wt %) and the PI WBAPO or BAPO (2.38 mmol/100 g resin) was studied by photo-DSC using a blue LED (emission spectrum: 380–515 nm, λmax = 460 nm) as irradiation source. The Photo-DSC plots

N-alkyl-N-(phosphonoethyl) substituted (meth)acrylamides – new adhesive monomers for self-etching self-priming one part dental adhesive

• Joachim E. Klee and
• Uwe Lehmann

Beilstein J. Org. Chem. 2009, 5, No. 72, doi:10.3762/bjoc.5.72

• /141.2 ppm (3d), 121.7/140.2 ppm (3h). Absorptions of the P-OH moiety were found at 1078, 3390 and 3411 cm−1 (3c, 3d). DSC investigation of 3 The polymerization behavior of N-alkyl-N-(phosphonoethyl)acrylamides and methacrylamides 3 was investigated by photopolymerization using a DSC7/DPA7 unit. The

• photochemically or thermally with AIBN as initiator. The methacrylamides 3 exhibit a relatively strong delay of photopolymerization. The thermal initiated polymerization with AIBN leads to relatively low polymerization enthalpies ranging from −8.57 (3b) to −25.1 (3h) kJ·mol−1 per double bond only, which are

• photopolymerization. Surprisingly, phosphonic acid 3c shows the highest adhesion to both enamel and dentin. Probably, 3c fulfils better than the other monomers some of the essential conditions for high adhesion to both tooth substrates such as the presence of hydrophilic/hydrophobic moieties of the adhesive molecule