WO2025064220A1

WO2025064220A1 - Photocurable organopolysiloxane resin

Info

Publication number: WO2025064220A1
Application number: PCT/US2024/045237
Authority: WO
Inventors: Junying Liu; Robert David GRIGG; Jordan C. REDDEL; Jonathan AXTELL; Sukrit MUKHOPADHYAY; Souvagya BISWAS
Original assignee: Dow Global Technologies Llc; Dow Silicones Corporation
Priority date: 2023-09-22
Filing date: 2024-09-05
Publication date: 2025-03-27
Also published as: TW202513718A

Abstract

The present invention is a composition comprising a bisacylphosphine oxide photoinitiator, a mercapto-C₃-C₁₂-alkyl functionalized organopolysiloxane, and an alkene functionalized organopolysiloxane, as described herein. The composition of the present invention provides homogeneous coatings that achieve acceptable cure depths by UV or LED irradiation.

Description

Photocurable Organopolysiloxane Resin Background of the Invention The present invention relates to a photocurable polyorganosiloxane resin and a bisacylphosphine oxide photoinitiator. UV or LED initiated curing of polymers is desirable for high throughput processing. Curing is induced by a photoinitiator that is compatible with the polymers; for organopolysiloxane curing systems, however, compatibility is a long-standing and heretofore unsolved problem. Photoinitiators with poor compatibility are undesirable as curing agents because they separate from the silicone matrix during storage, resulting in ineffective cure, undesired haze, and coating defects of the cured product. US 10,597,413 B2 (Tan) describes an acyl phosphine oxide substituted with -CH2-O-Si(OR)3 groups, a typical example of which is the following compound: Si Although Tan discloses that these

photoinitiators address a long-standing solubility problem, it is evident that another problem is introduced, namely susceptibility to acid cleavage of the silyl ether bond (CH2-OSi), thereby rendering the photoinitiator incompatible with the silicone matrix. It would therefore be an advantage in the art of photoinitiation in silicone systems to achieve solubility and with maintenance of stability. Summary of the Invention The present invention addresses a need in the art by providing a composition comprising a bisacylphosphine oxide photoinitiator, a mercapto-C₃-C₁₂-alkyl functionalized organopolysiloxane, and an alkene functionalized organopolysiloxane, wherein the bisacylphosphine oxide photoinitiator is a compound of Formula 1: where m is 0, 1, 2, or 3; and n is 0, 1

R¹ is -phenyl-(R³)_n, -C(O)-phenyl-(R²)_m, -O-C₁-C₂₀-alkyl, or -O(CH₂CH₂O)_x-H, where x is from 1 to 20; each R² is independently C₁-C₆-alkyl; C₁-C₆-alkoxy; -OCH₂-phenyl; or R² together with an adjacent R² on the phenyl ring is a 1,3-dioxolane group or a 1,4-dioxane group; each R³ is independently C1-C6-alkyl or C1-C6-alkoxy; R⁴ is i) –(Si(Me )) ( 5 2 p CH2)q(Si(R 2)O)r(X)s-Y; where p is 0 or 1 with the proviso that when p is 0, q is 3 to 12, and when p is 1, q is 2 to 12; r is from 3 to 300; X is CH₂CH₂ or CH(CH₃); s is 0 or 1 with the proviso that when s is 0, Y is SiMe₂H, and when s is 1, Y is Si(OMe)₃; SiMe₃; Si(OEt)3; SiMe2OMe; SiMe2OEt; Si(OSiMe3)3; SiMe(OSiMe3)2; SiMe2(OSiMe3); or ;

where the dashed line is the point of attachment from Y to X; and each R⁵ is independently C1-C6-alkyl or phenyl; or R⁴ is ii) –(Si(Me2))p(CH2)t-Z; where p is 0 or 1 with the proviso that when p is 0, t is 4 and when p is 1, t is 2; and Z is either: where the dashed line is the

po nt o attac ment rom to ( 2)t. The composition of the present invention addresses a need in the art by providing an organopolysiloxane composition that can be cured by UV or LED to form a haze free, defect free coating.

Detailed Description of the Invention The present invention is a composition comprising a composition comprising a bisacylphosphine oxide photoinitiator, a mercapto-C₃-C₁₂-alkyl functionalized organopolysiloxane, and an alkene functionalized organopolysiloxane, wherein the bisacylphosphine oxide photoinitiator is a compound of Formula 1: where m is 0, 1, 2, or 3; and n is 0, 1

; R¹ is -phenyl-(R³)_n, -C(O)-phenyl-(R²)_m, -O-C₁-C₂₀-alkyl, or -O(CH₂CH₂O)_x-H, where x is from 1 to 20; each R² is independently C1-C6-alkyl; C1-C6-alkoxy; -OCH2-phenyl; or R² together with an adjacent R² on the phenyl ring is a 1,3-dioxolane group or a 1,4-dioxane group; each R³ is independently C1-C6-alkyl or C1-C6-alkoxy; R⁴ is i) –(Si(Me 5 2))p(CH2)q(Si(R 2)O)r(X)s-Y; where p is 0 or 1 with the proviso that when p is 0, q is 3 to 12, and when p is 1, q is 2 to 12; r is from 3 to 300; X is CH₂CH₂ or CH(CH₃); s is 0 or 1 with the proviso that when s is 0, Y is SiMe₂H, and when s is 1, Y is Si(OMe)₃; SiMe₃; Si(OEt)3; SiMe2OMe; SiMe2OEt; Si(OSiMe3)3; SiMe(OSiMe3)2; SiMe2(OSiMe3); or ; where the dashed line is the point of a

to X; and each R⁵ is independently C1-C6-alkyl or phenyl; or R⁴ is ii) –(Si(Me2))p(CH2)t-Z; where p is 0 or 1 with the proviso that when p is 0, t is 4 and when p is 1, t is 2; and Z is either:

where the dashed line is the point of attachment from Z to (CH2)t. In one aspect, R¹ is -C(O)-phenyl-(R²)m. An example of a preferred R¹ group is represented by the following structure:

In one aspect, R⁴ is –(Si(Me2))p(CH2)q(Si(R5 2)O)r(X)s-Y; in another aspect, each R⁵ is methyl. In one aspect, when p is 0, q is 3 or 4; in another aspect, when p is 1, q is 2; r is from 3 or from 6 or from 10, to 300 or to 200 or to 100 or to 50. The compound of Formula I can be prepared as described in Schemes 1 to 3. Where R¹ is -C(O)-phenyl-(R²)_m, and R⁴ is in the para position of benzene ring, the compound of Formula I can be prepared in accordance with Scheme 1. The reaction conditions for each step are described in the experimental section. Scheme 1

where q' is 1 to 10 when p is 0, and q' is 0 to 10 when p is 1.

Alternatively, where R¹ is -C(O)-phenyl-(R²)_m, the compound of the present invention can be prepared by reacting the final Intermediate with either compound A or B:

where X is CH₂CH₂ or CH(CH₃). Where p is 1, the first compound in Scheme 1 can be prepared by contacting in a first step a dibromobenzene, particularly p-dibromobenzene, with a vinyl dimethylsilyl chloride in the presence of n-butyl lithium to form the following intermediate: where b is from 0 to 10.

Where p is 0, the first compound, especially where q′ is 2, can be prepared as described in Li, Y.-L.; Song, D.-P.; Pan, L.; Ma, Z.; Li, Y.-S. Polym. Chem.2019, 10, 6368-6378. Where R¹ is -O-C₁-C₂₀-alkyl, or -O(CH₂CH₂O)_x-H, the compound of Formula I can be prepared in accordance with Scheme 2.

Scheme 2

Where R¹ is -phenyl-(R³)n , the compound of Formula I can be prepared in accordance with Scheme 3. Scheme 3

The concentration of photoinitiator core portion of the photoinitiator is typically in the range of from 0.01 wt.% or from 0.05 wt%, or from 0.1 wt% to 10 wt% or to 4 wt.% or to 2 wt.%, based on the weight of the composition. As used herein, “photoinitiator core” refers to the following fragment of the bisacylphosphine oxide photoinitiator:

where q′ is 1 to 10 when p is 0, and q′ is 0 to 10 when p is 1. The mercapto-C₃-C₁₂-alkyl functionalized organopolysiloxane may be linear or branched. For example, the mercapto-C3-C12-alkyl functionalized organopolysiloxane may contain one or more silicon atoms attached to two oxygen atoms and two C₁-C₆-alkyl groups, two phenyl groups, or one C1-C6-alkyl and one phenyl group (“D” units); one or more silicon atoms attached to three oxygen atoms and one C₁-C₆-alkyl group or one phenyl group (“T” units), or one or more silicon atoms attached to three oxygen atoms (“Q” units). An example of a class of mercapto-C3-C12- alkyl functionalized organopolysiloxanes comprising D units is represented by Formula 2:

where each R^1′ is -CH2CH2(CH2)z-SH; each R^2′ is independently methyl or -CH2CH2(CH2)z-SH; x is from 2 to 1000; y is from 0 to 100; and each z is from 1 to 10, with the proviso that when y is 0, at least one of the R^2′ groups is -CH2CH2(CH2)z-SH; and with the further proviso that when each R^2′ is methyl, y is from 1 to 100. Preferably, z is from 1 to 8; more preferably, z is from 1 to 4; most preferably, z is 1. Preferably, x is from 10 or from 20, to 500 or to 100. Preferably, when y is 0, both R^2′ groups are -CH₂CH₂(CH₂)_z-SH groups; more preferably, when y is 0, both R^2′ groups are -CH2CH2CH2SH groups. Similarly, when both R^2′ groups are methyl, the R^1′ groups are preferably -CH₂CH₂CH₂SH groups. The concentration of the mercapto-C3-C12-alkyl functionalized organopolysiloxane is typically in the range of from 1 or from 3 weight percent, to 70 or to 30 or to 20 weight percent, based on the combined weights of the mercapto-C3-C12-alkyl functionalized organopolysiloxane and the alkene functionalized organopolysiloxane. Examples of alkene functionalized organopolysiloxanes include divinyl, diallyl, and dihexenyl functionalized organopolysiloxanes. An example of a divinyl functionalized polydimethylsiloxane is shown in Formula 3:

where a is from 10 to 10,000. The concentration of the alkene functionalized organopolysiloxanes is typically in the range of 5 or from 30 or from 70 weight percent, to 99 or to 90 weight percent, based on the combined weights of the mercapto-C3-C12-alkyl functionalized organopolysiloxane and the alkene functionalized organopolysiloxane. Commercially available organopolysiloxanes include XIAMETER™ RBL-9119 Organopolysiloxane and XIAMETER™ RBL-9128 Organopolysiloxane (XIAMETER is a Trademark of The Dow Chemical Company or its Affiliates.) Another example of an alkene functionalized organopolysiloxane comprises an organopolysiloxane with Si-C₁-C₆-alkoxysilyl functionality and Si-alkenyl functionality, which may be used in addition to a compound of Formula 3 or place of it. Examples of organopolyiloxanes with Si-C₁-C₆-alkoxysilyl functionality and Si-alkenyl functionality are disclosed in WO 2020/076620 A1. One such dual functional compound is the compound of Formula 4:

Formula 4 where b is from 1 to 5000.

Additionally, the composition may further comprise an organopolysiloxane with Ci-Ce- alkoxysilane groups.

Where moisture cure is desired, the composition advantageously comprises a moisture cure catalyst such as a titanium catalyst, and example of which is titanium dioxide acetoacetate complex, commercially available as Tyzor PITA-SM Organic Titanate.

The composition of the present invention is capable of undergoing UV cure or moisture cure with the inclusion of a single compound with dual Si-alkenyl/Si-alkoxy functionality or a mixture of compounds with Si-alkenyl and Si-alkoxy functionalities.

Examples

Intermediate Example 1 - Preparation of M'DuM' Polysiloxane Substituted Photoinitiator

A. Preparation of (4-(But-3-en-l-yl)phenyl)dichlorophosphane

In a glovebox, a 500 mL round bottom flask was charged with l-bromo-4-(but-3-en-l- yl)benzene (17.1 g), dry THF (118 mL), and dry diethyl ether (37 mL). The flask was sealed and transferred to a fume hood. The mixture was stirred under N2 and cooled to -78 °C, then n-butyllithium (n-BuLi, 2.5 M in hexane, 34.0 mL) was added dropwise to the mixture. The mixture stirred for 30 min, after which time chlorobis(diethylamino)phosphine (17.9 mL, 85.1 mmol). The mixture stirred for 20 min and was allowed to warm to ambient temperature. The solution was poured into a separatory funnel containing diethyl ether and water. The phases were separated, and the aqueous phase was extracted with a few portions of diethyl ethyl ether. The combined organic fractions were washed with brine, dried over MgSCh and concentrated in vacuo.

The crude oil was transferred to a 1000-mL round bottom flask, which was placed in a glovebox. The oil was dissolved in dry diethyl ether (100 mL). The mixture was stirred and treated with HC1 (2.0 M in diethyl ether, 162 mL, 324 mmol, 4.00 equiv) dropwise, and a white solid precipitated. After 2 h, the slurry was filtered and the filtrate was concentrated. A colorless oil was isolated (15.9 g, 84%), which was used in the next step without further purification.

B. Preparation of (4-(But-3-en-l-yl)phenyl)phosphane

In a glovebox, a 500 mL jar was charged with diethyl ether (100 mL) and Li Al Hr (2.0 M in THF, 19.8 mL, 39.6 mmol, 0.60 eq.). The solution was stirred vigorously, and (4-(but-3-en-l-yl)phenyl)dichlorophosphane (15.4 g, 66.1 mmol, 1.00 eq.) in diethyl ether (65 mL) was added to the solution dropwise over 10 min. The mixture stirred for 30 min before solid Glauber Salt (25.5 g, 79.3 mmol, 1.20 eq.) was cautiously added. The mixture stirred for 60 min, and the liquid was decanted and filtered through a 0.45 pm syringe filter and concentrated to give a colorless oil (9.73 g, 90%), which was used in the next step without further purification.

C. Preparation of ((4-(But-3-en-l-yl)phenyl)phosphoryl)bis(mesitylmethanone)

In a glovebox, a solution of Preparation of (4-(But-3-en-l-yl)phenyl)phosphane (9.73 g,

59.3 mmol, 1.00 eq.) in dry THF (300 mL) was treated with sodium tert-butoxide (NatOBu,

11.4 g, 118 mmol, 2.00 eq.), then 2,4,6-trimethylbenzoyl chloride (19.8 mL, 118 mmol, 2.00 eq.) was added drop wise to the mixture. The mixture was stirred overnight. Crude ³¹ P NMR spectroscopic analysis indicated that the phosphine was partially consumed. An additional amount of Na/OBu (3.99 g) and the benzoyl chloride (6.9 mL) were added to the reaction mixture. After 5 h, the mixture was filtered to remove sodium chloride, and the filtrate was removed from the glovebox and concentrated in vacuo. The crude residue was dissolved in dichloromethane (200 mL), and the solution was treated with hydrogen peroxide (6.0 mL 30 wt.%). The mixture was stirred overnight at ambient temperature, then treated with aqueous sodium bisulfite solution (100 mL) and stirred until the organic phase was negative to a peroxide strip test. Phases were separated and concentrated with celite for chromatography on silica gel (0 to 50% EtOAc in hexane). A yellow oil (13 g) that contained product and some other impurities was isolated. A second column purification was performed, whereupon Intermediate Example 3 (11.3 g) was isolated as a yellow oil.

D. Preparation of M'DuM' Polysiloxane Substituted Photoinitiator

Preparation of ((4-(But-3-en-l-yl)phenyl)phosphoryl)bis(mesitylmethanone) (0.07 g) was mixed with dry hexane (3.0 mL) and M'DMM' Polysiloxane (0.99 g) in a glovebox. The mixture was stirred at 50 °C until the solids dissolved. Karstedt’s Catalyst (2 wt% Pt in xylene, 0.03 mL) was added and the mixture was stirred overnight. Consumption of the alkene was monitored by ¹ H NMR spectroscopy, and additional portions of Karstedt’s Catalyst were added until <5% of the alkene remained. Vinyl trimethoxysilane was added to react with remaining Si-H groups. Volatiles were removed by vacuum pump, leaving an amber oil. A mixture of the following products was identified and calculated to comprise 4.0 wt% photoinitiator.

Intermediate Example 2 - Preparation of a M'DuM' Polysiloxane Substituted Photoinitiator

A. Preparation of (4-Bromophenyl)dimethyl(vinyl)silane

A 1000-mL 3-neck round bottom flask equipped with an addition funnel was charged with dry THF (425 mL) and 1,4-dibromobenzene (20.0 g, 84.8 mmol, 1.00 eq.) under a blanket of N2. The mixture was stirred at cooled to -78 °C. An n-BuLi solution (2.5 M in hexane, 35.6 mL, 89.0 mmol, 1.05 eq.) was added dropwise to the dibromobenzene solution over 25 min. Stirring was continued for another 50 min after the completion of addition of the n-BuLi solution.

Chlorodimethylvinylsilane (12.9 mL, 93.3 mmol, 1.10 equiv) was added dropwise to the reaction mixture with stirring. The mixture was gradually warmed to room temperature over 1 h, after which time the mixture was quenched with aqueous ammonium chloride. Product was extracted with several portions of ethyl acetate. Combined organic fractions were dried over sodium sulfate and concentrated. The crude oil was purified in vacuo (450 mTorr, 52-60 °C) to give (4-bromophenyl)dimethyl(vinyl)silane (18.75 g) as a colorless oil.

B. Preparation of ((4-(Dimethyl(vinyl)silyl)phenyl)phosphoryl)bis(mesitylmethanone)

In a glovebox, a 250-mL round bottom flask was charged with (4-Bromophenyl)dimethyl(vinyl)silane (4.31 g, 17.9 mmol, 1.00 eq.), dry THF (26 mL), and dry diethyl ether (8 mL). The flask was sealed and transferred to a fume hood. The mixture was stirred under nitrogen and cooled to -78 °C. whereupon n-BuLi (2.5 M in hexane, 7.51 mL, 18.8 mmol, 1.05 eq.) was added dropwise. The mixture stirred for 30 min, after which time chlorobis(diisopropylamino)phosphine (5.01 g, 18.8 mmol, 1.05 eq.) was added as a solid. The mixture was stirred and allowed to warm to ambient temperature over 2 h. The solution was poured into a separatory funnel containing diethyl ether and water. The phases were separated, and the aqueous phase was extracted with a few portions of diethyl ethyl ether. The combined organic fractions were washed with brine, dried with MgSCU and concentrated by rotary evaporation.

The crude oil was transferred to a 250-mL round bottom flask, which was placed in a glovebox. The oil was dissolved in dry diethyl ether (20 mL). The flask was sealed and transferred to a fume hood. The mixture was stirred and cooled to 0 °C under N2. HC1 (2.0 M in diethyl ether, 35.7 mL, 71.5 mmol, 4.00 eq.) was then added dropwise and a white solid precipitated. After continued stirring for 2 h, the slurry was filtered and the fdtrate concentrated. The crude residue was mixed with diethyl ether and hexane and filtered again. The filtrate was concentrated to give a colorless oil (4.59 g). The crude material was used in the next step without further purification.

In a glovebox, a 150-mL jar was charged under vigorous stirring with diethyl ether (44 mL) and L1A1H4 (2.0 M in THF, 5.23 mL, 10.5 mmol, 0.60 eq.). The crude material from the previous step (4.59 g, 17.4 mmol, 1.00 equiv) was added to the LiAlfL solution dropwise over 5 min.

The mixture stirred for 30 min, after which time solid Glauber Salt (6.74 g, 20.9 mmol, 1.20 eq.) was cautiously added. Stirring continued for 14 h, after which time the solution was filtered and the filtrate concentrated to give 2.71 g of crude product as a colorless oil. The crude material was used in the next step without further purification.

A solution of the crude material from the previous step (2.71 g) in dry THF (70 mL) was treated with dry Na/OBu (2.68 g, 27.9 mmol, 2.00 eq.), followed by dropwise addition of 2,4,6-trimethylbenzoyl chloride (4.65 mL, 27.9 mmol, 2.00 eq.). The mixture stirred for 3 h and the mixture was then filtered to remove sodium chloride.

The filtrate was removed from the glovebox and concentrated in vacuo. The crude residue was dissolved in dichloromethane (50 mL), and the solution was treated with hydrogen peroxide (1.4 mL, 30 wt.%). The mixture was stirred overnight at ambient temperature, then treated with aqueous sodium bisulfite solution (30 mL). Phases were separated and the organic phase was concentrated in the presence of silica gel to facilitate liquid chromatography on silica gel (0 to 50% EtOAc in hexane). ((4-(Dimethyl(vinyl)silyl)phenyl)phosphoryl)bis(mesitylmethanone) (1.98 g) was isolated as a yellow oil that solidified upon standing.

C. Preparation of a M'DuM' Polysiloxane Substituted Photoinitiator

((4-(Dimethyl(vinyl)silyl)phenyl)phosphoryl)bis(mesitylmethanone) (0.10 g) was mixed with dry toluene (1.5 mL) and M'DuM' Polysiloxane (0.24 g) in a glovebox. The mixture was stirred at 80 °C until the solids dissolved. Karstedt’s Catalyst (2 wt% Pt in xylene, 0.012 mL) was added to the mixture and stirring was continued for 1 h. Consumption of the alkene was monitored by ¹ H NMR spectroscopy, and additional portions of Karstedt’s Catalyst were added until <5% of the alkene remained. Vinyl trimethoxy silane was added to react with remaining Si-H groups. Volatiles were remove in vacuo leaving an amber oil. A mixture of the following products was identified and calculated to comprise 30.0 wt% photoinitiator.

Example 1 - Preparation of a Dual Curable Organopolysiloxane Composition

A dual curable organopolysiloxane composition was prepared by blending together in a 100-mL dental cup the compound of Formula 2 (7.05 pbw, each R² is methyl, R¹ is HS-CH2CH2CH2-, x = 5, y = 43; the compound of Formula 3 (40.66 pbw, a = 766); the compound of Formula 4 (28.4 pbw, each b = 30; and fumed silica filler (17.43 pbw). The blend was mixed at 1000 rpm for 20 s, then further mixed at 2000 rpm for 45 s. A mixture of methyltrimethoxysilane (3.74 pbw) and butylated hydroxytoluene (0.56 pbw) was added to the blend, and mixing was continued at 2000 rpm for 30 s. Methyltrimethoxysilane (0.5 pbw), Intermediate Example 1 photoinitiator (1.03 pbw) and Tyzor PITA-SM (0.10 pbw) were then added to the blend, and mixing was continued at 2000 rpm for 30 s. The composition was then packaged in three 30-mL syringes and deaired, then vacuum sealed in an aluminum bag to avoid moisture and light.

Example 2 - Preparation of a Dual Curable Organopolysiloxane Composition

The preparation described in Example 1 was carried out in substantially the same way except that Intermediate Example 2 photoinitiator (1.03 pbw) was used.

Comparative Example 1 - Preparation of a Dual Curable Organopolysiloxane Composition The preparation described in Example 1 was carried out in substantially the same way except that Irgacure 819 bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide photoinitiator (1.03 pbw, Irgacure 819) was used.

UV Cure Procedure

The samples were cured using a Colight UV curing oven equipped with a mercury lamp at an intensity of 300 mW/cm² and 2J/cm² dosage of UVA and UVB wavelengths.

LED Cure Procedure

The samples were cured using Uvitron Skyray 800 LED Flood Curing System with a 365-nm LED oven with an intensity of 500 mW/cm² and an irradiation dosage of 10 J/cm².

UV Cure Depth Measurement

Formulations were filled into a Teflon block with wells having diameters of 25 mm and depths of 20 mm. The coating was exposed to UV irradiation or LED irradiation. The samples were removed from the wells and uncured material was removed with a tissue so that cure depth could be measured with a ruler.

Table 1 illustrates the formulation appearance, the coating appearance, and the cure depth of the samples cured by UV irradiation. A cure depth of >3 mm was considered acceptable.

Table 1 - Cure Depth and Appearance for UV Irradiated Formulations

Precipitated particles were apparent in the formulation appearance of comparative example 1 , resulting in an inhomogeneous coating upon cure with aggregation defect; in contrast, the example formulations of the present invention formed stable emulsions with no visible signs of precipitated particles, and the consequent coatings were homogeneous.

Table 2 illustrates the formulation appearance, the coating appearance, and the cure depth of the samples cured by LED irradiation. A cure depth of >3 mm was considered acceptable. Table 2 - Cure Depth and Appearance for LED Irradiated Formulations

The data shows that the composition containing the photoinitiator of the present invention gave homogenous formulations and coatings and acceptable cure depth for both types of irradiations. In contrast, the composition containing Irgacure 819 photoinitiator was inhomogeneous and gave an inhomogeneous coating.

Claims

Claims: 1. A composition comprising a bisacylphosphine oxide photoinitiator, a mercapto-C3-C12-alkyl functionalized organopolysiloxane, and an alkene functionalized organopolysiloxane, wherein the bisacylphosphine oxide photoinitiator is a compound of Formula 1: where m is 0, 1, 2, or 3; and n is 0, 1

; R¹ is -phenyl-(R³)_n, -C(O)-phenyl-(R²)_m, -O-C₁-C₂₀-alkyl, or -O(CH₂CH₂O)_x-H, where x is from 1 to 20; each R² is independently C1-C6-alkyl; C1-C6-alkoxy; -OCH2-phenyl; or R² together with an adjacent R² on the phenyl ring is a 1,3-dioxolane group or a 1,4-dioxane group; each R³ is independently C₁-C₆-alkyl or C₁-C₆-alkoxy; R⁴ is i) –(Si(Me₂))_p(CH₂)_q(Si(R5₂)O)_r(X)_s-Y; where p is 0 or 1 with the proviso that when p is 0, q is 3 to 12, and when p is 1, q is 2 to 12; r is from 3 to 300; X is CH2CH2 or CH(CH3); s is 0 or 1 with the proviso that when s is 0, Y is SiMe2H, and when s is 1, Y is Si(OMe)3; SiMe3; Si(OEt)₃; SiMe₂OMe; SiMe₂OEt; Si(OSiMe₃)₃; SiMe(OSiMe₃)₂; SiMe₂(OSiMe₃); or ; where the dashed line is the point of a

to X; and each R⁵ is independently C1-C6-alkyl or phenyl; or R⁴ is ii) –(Si(Me₂))_p(CH₂)_t-Z; where p is 0 or 1 with the proviso that when p is 0, t is 4 and when p is 1, t is 2; and Z is either:

where the dashed line is the point of attachment from Z to (CH₂)_t. 2. The composition of Claim 1 where the mercapto-C3-C12-alkyl functionalized organopolysiloxane is represented by Formula 2:

where each R^1′ is -CH2CH2(CH2)z-SH; each R^2′ is independently methyl or -CH2CH2(CH2)z-SH; x is from 2 to 1000; y is from 0 to 100; and each z is from 1 to 10, with the proviso that when y is 0, at least one of the R^2′ groups is -CH2CH2(CH2)z-SH; and with the further proviso that when each R^2′ is methyl, y is from 1 to 100; and the alkene functionalized organopolysiloxane is represented by Formula 3:

where a is from 10 to 10,000. 3. The composition of Claim 2 wherein z is 1; R¹ is -C(O)-phenyl-(R²)m; each R² is methyl, each m is 3, each n is 0, and R⁴ is –(Si(Me2))p(CH2)q(Si(R5 2)O)r(X)s-Y, where each R⁵ is methyl, X is CH2CH2, r is 10 to 200; q is 3 when p is 0, q is 2 when p is 1; and Y is Si(OMe)3 or where the dashed line is the poin

t of attachment from to the CH2CH2 group. 4. The composition of Claim 2 wherein z is 1; R¹ is -C(O)-phenyl-(R²)m; each R² is methyl, each m is 3, each n is 0, and R⁴ is –(Si(Me₂))_p(CH₂)_t-Z. 5. The composition of Claim 1 wherein z is 1; R¹ is -C(O)-phenyl-(R²)m; each R² is methyl, each m is 3, each n is 0, and R⁴ is –(Si(Me₂))_p(CH₂)_q(Si(R5₂)O)_r(X)_s-Y, where each R⁵ is methyl, X is CH2CH2, r is 10 to 200; q is 3 when p is 0, q is 2 when p is 1; and Y is Si(OMe)3 or where the dashed line is the point

CH2CH2 group; and wherein the alkene functionalized organopolysiloxane is further functionalized with Si-C1-C6-alkoxysilyl groups. 6. The composition of any of Claims 2 to 4 which further comprises an organopolysiloxane functionalized with Si-C₁-C₆-alkoxysilyl groups. 7. The composition of Claim 6 wherein the organopolysiloxane functionalized with Si-C₁-C₆- alkoxysilyl groups is further functionalized with Si-vinyl groups, wherein the C1-C6-alkoxysilyl groups are trimethoxysilyl groups. 8. The composition of Claim 7 wherein the organopolysiloxane functionalized with trimethoxysilyl groups and vinyl groups is represented by the following formula:

where b is from 1 to 5000. 9. The composition of Claim 1 wherein the bisacylphosphine oxide photoinitiator is selected from the group consisting of

where r is from 6 to 50. 10. The composition of Claim 8 wherein the bisacylphosphine oxide photoinitiator is selected from the group consisting of

where r is from 6 to 50.